Resist composition and method of forming resist pattern

ABSTRACT

A resist composition including a polymeric compound having 0 to 20 mol % of a structural unit containing a polar group-containing aliphatic hydrocarbon group, and an acid generator compound represented by general formula (b1-1) in which R 101  represents a hydrocarbon group having at least 1 hydroxy group as a substituent; Y 101  represents a single bond or a divalent linking group containing an oxygen atom; V 101  represents a single bond, an alkylene group or a fluorinated alkylene group; R 102  represents a fluorine atom or a fluorinated alkyl group of 1 to 5 carbon atoms; M′ m+  represents an organic cation having a valency of m.

TECHNICAL FIELD

The present invention relates to a resist composition and a method offorming a resist pattern.

This application claims priority to Japanese Patent Application No.2016-183517, filed Sep. 20, 2016, the entire content of which isincorporated herein by reference.

DESCRIPTION OF RELATED ART

In lithography techniques, for example, a resist film composed of aresist material is formed on a substrate, and the resist film issubjected to selective exposure, followed by development, therebyforming a resist pattern having a predetermined shape on the resistfilm. A resist material in which the exposed portions of the resist filmbecome soluble in a developing solution is called a positive-type, and aresist material in which the exposed portions of the resist film becomeinsoluble in a developing solution is called a negative-type.

In recent years, in the production of semiconductor elements and liquidcrystal display elements, advances in lithography techniques have led torapid progress in the field of pattern miniaturization.

Typically, these miniaturization techniques involve shortening thewavelength (increasing the energy) of the exposure light source.Conventionally, ultraviolet radiation typified by g-line and i-lineradiation has been used, but nowadays KrF excimer lasers and ArF excimerlasers are starting to be introduced in mass production. Furthermore,research is also being conducted into lithography techniques that use anexposure light source having a wavelength shorter (energy higher) thanthese excimer lasers, such as electron beam (EB), extreme ultravioletradiation (EUV), and X ray.

Resist materials for use with these types of exposure light sourcesrequire lithography properties such as a high resolution capable ofreproducing patterns of minute dimensions, and a high level ofsensitivity to these types of exposure light sources.

Conventionally, as a resist material that satisfies these conditions, achemically amplified composition is used, which includes anacid-generator component that generates acid upon exposure and a basematerial component that exhibits a changed solubility in a developingsolution under the action of acid.

As the base component used in a chemically amplified resist composition,a resin (base resin) is generally used.

For example, in the case of forming a positive-tone resist pattern by analkali developing process using an alkali developing solution as thedeveloping solution, a chemically amplified resist which contains anacid generator and a resin composition that exhibits increasedsolubility in an alkali developing solution by the action of acid isgenerally used. If the resist film formed using the resist compositionis selectively exposed during formation of a resist pattern, then withinthe exposed portions, acid is generated from the acid-generatorcomponent, and the action of this acid causes an increase in thesolubility of the resin component in an alkali developing solution,making the exposed portions soluble in the alkali developing solution.Thus, by conducting alkali developing, the unexposed portions remain toform a positive resist pattern.

As the resin component, a resin that exhibits increased polarity by theaction of acid is generally used. As the resin that exhibits increasedpolarity by the action of acid, a resin which has a structural unitcontaining an acid decomposable group (hereafter, sometimes referred toas “protection group”) that exhibits increased polarity by the action ofacid is used.

When the polarity increases, the solubility of the resin in an alkalideveloping solution is increased, whereas the solubility of the resin inan organic solvent decreases. Therefore, when such a base resin isapplied to a solvent developing process using a developing solutioncontaining an organic solvent (organic developing solution) instead ofan alkali developing process, the solubility of the exposed portions inan organic developing solution is decreased. As a result, in the solventdeveloping process, the unexposed portions of the resist film aredissolved and removed by the organic developing solution, and a negativeresist pattern in which the exposed portions are remaining is formed.Such a solvent developing process for forming a negative-tone resistcomposition is sometimes referred to as “negative-tone developingprocess” (for example, see Patent Literature 1).

Currently, as the base resin of a chemically amplified resistcomposition which is used in ArF excimer laser lithography, in terms ofthe advantages in the vicinity of 193 nm, a resin which has a structuralunit derived from (meth)acrylate ester in the main chain thereof(acrylic resin) is generally used (see for example, Patent Literatures 2and 3).

Here, the term “(meth)acrylate ester” is a generic term that includeseither or both of the acrylate ester having a hydrogen atom bonded tothe α-position and the methacrylate ester having a methyl group bondedto the α-position. The term “(meth)acrylate” is a generic term thatincludes either or both of the acrylate having a hydrogen atom bonded tothe α-position and the methacrylate having a methyl group bonded to theα-position. The term “(meth)acrylic acid” is a generic term thatincludes either or both of acrylic acid having a hydrogen atom bonded tothe α-position and methacrylic acid having a methyl group bonded to theα-position.

On the other hand, as acid generators usable in a chemically amplifiedresist composition, various types have been proposed including, forexample, onium salt acid generators; oxime sulfonate acid generators;diazomethane acid generators; nitrobenzylsulfonate acid generators;iminosulfonate acid generators; and disulfone acid generators.

Among these, as the onium salt acid generators, iodonium salts having aniodonium ion as the cation or sulfonium salts having a sulfonium ion asthe cation have been conventionally used. As the anion (acid) whichforms a salt with such cations, a fluorinated alkylsulfonic acid ion istypically used (see for example, Patent Literature 4).

DOCUMENTS OF RELATED ART Patent Literature

[Patent Document 1] Japanese Unexamined Patent Application, FirstPublication No. 2008-292975

[Patent Document 2] Japanese Unexamined Patent Application, FirstPublication No. 2003-241385

[Patent Document 3] Japanese Unexamined Patent Application, FirstPublication No. 2009-169228

[Patent Document 4] Japanese Unexamined Patent Application, FirstPublication No. 2005-037888

SUMMARY OF THE INVENTION

As further progress is expected to be made in lithography techniques andthe application field for lithography techniques is expected to expand,development of a novel material for use in lithography will be desired.

However, as the miniaturization of the pattern progresses, there wasstill room for improvement of conventional resist compositions in termsof lithography properties such as resolution, exposure latitude (ELmargin), CDU and the like.

The present invention takes the above circumstances into consideration,with an object of providing a resist composition which exhibits goodlithography properties, and a method of forming a resist pattern,

A first aspect of the present invention is a resist composition whichgenerates acid upon exposure and exhibits changed solubility in adeveloping solution under action of acid, the resist compositionincluding a base component (A) which exhibits changed solubility in adeveloping solution under action of acid and an acid generator (B) whichgenerates acid upon exposure, the base component (A) including apolymeric compound (A1) containing 0 to 20 mol % of a structural unit(a3) containing a polar group-containing aliphatic hydrocarbon group,and the acid generator component (B) containing an acid generator (B1)consisting of a compound represented by general formula (b1-1) shownbelow.

In the formula, R¹⁰¹ represents a hydrocarbon group having at least 1hydroxy group as a substituent; Y¹⁰¹ represents a single bond or adivalent linking group containing an oxygen atom; V¹⁰¹ represents asingle bond, an alkylene group or a fluorinated alkylene group; R¹⁰²represents a fluorine atom or a fluorinated alkyl group of 1 to 5 carbonatoms; and M′^(m+) represents an organic cation having a valency of m.

A second aspect of the present invention is a method of forming a resistpattern, including: using a resist composition according to the firstaspect to form a resist film on a substrate, subjecting the resist filmto exposure, and subjecting the exposed resist film to developing toform a resist pattern.

According to the present invention, there are provided a resistcomposition which exhibits good lithography properties, and a method offorming a resist pattern.

DETAILED DESCRIPTION OF THE INVENTION

In the present description and claims, the term “aliphatic” is arelative concept used in relation to the term “aromatic”, and defines agroup or compound that has no aromaticity.

The term “alkyl group” includes linear, branched or cyclic, monovalentsaturated hydrocarbon, unless otherwise specified.

The term “alkylene group” includes linear, branched or cyclic, divalentsaturated hydrocarbon, unless otherwise specified. The same applies forthe alkyl group within an alkoxy group.

A “halogenated alkyl group” is a group in which part or all of thehydrogen atoms of an alkyl group is substituted with a halogen atom.Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom.

A “fluorinated alkyl group” or a “fluorinated alkylene group” is a groupin which part or all of the hydrogen atoms of an alkyl group or analkylene group have been substituted with a fluorine atom.

The term “structural unit” refers to a monomer unit that contributes tothe formation of a polymeric compound (resin, polymer, copolymer).

A “structural unit derived from an acrylate ester” refers to astructural unit that is formed by the cleavage of the ethylenic doublebond of an acrylate ester.

An “acrylate ester” refers to a compound in which the terminal hydrogenatom of the carboxy group of acrylic acid (CH₂═CH—COOH) has beensubstituted with an organic group.

The acrylate ester may have the hydrogen atom bonded to the carbon atomon the α-position substituted with a substituent. The substituent(R^(α)) with which the hydrogen atom bonded to the carbon atom at theα-position is substituted is an atom other than the hydrogen atom or agroup, and examples thereof include an alkyl group having from 1 to 5carbon atoms, a halogenated alkyl group having from 1 to 5 carbon atoms,and a hydroxyalkyl group. A carbon atom on the α-position of an acrylateester refers to the carbon atom bonded to the carbonyl group, unlessspecified otherwise.

Hereafter, an acrylate ester having the hydrogen atom bonded to thecarbon atom on the α-position substituted with a substituent issometimes referred to as “α-substituted acrylate ester”. Further,acrylate esters and α-substituted acrylate esters are collectivelyreferred to as “(α-substituted) acrylate ester”.

As the alkyl group as a substituent on the α-position, a linear orbranched alkyl group is preferable, and specific examples include alkylgroups of 1 to 5 carbon atoms, such as a methyl group, an ethyl group, apropyl group, an isopropyl group, an n-butyl group, an isobutyl group, atert-butyl group, a pentyl group, an isopentyl group and a neopentylgroup.

Specific examples of the halogenated alkyl group as the substituent onthe α-position include groups in which part or all of the hydrogen atomsof the aforementioned “alkyl group as the substituent on the α-position”are substituted with halogen atoms. Examples of the halogen atom includea fluorine atom, a chlorine atom, a bromine atom and an iodine atom, anda fluorine atom is particularly desirable.

Specific examples of the hydroxyalkyl group as the substituent on theα-position include groups in which part or all of the hydrogen atoms ofthe aforementioned “alkyl group as the substituent on the α-position”are substituted with a hydroxy group. The number of hydroxy groupswithin the hydroxyalkyl group is preferably 1 to 5, and most preferably1.

The case of describing “may have a substituent” includes both of thecase where the hydrogen atom (—H) is substituted with a monovalent groupand the case where the methylene group (—CH₂—) is substituted with adivalent group.

The term “exposure” is used as a general concept that includesirradiation with any form of radiation.

(Resist Composition)

A first aspect of the present invention is a resist composition whichgenerates acid upon exposure and exhibits changed solubility in adeveloping solution under action of acid, the resist compositionincluding a base component (A) (hereafter, sometimes referred to as“component (A)”) which exhibits changed solubility in a developingsolution under action of acid and an acid generator (B) (hereafter,sometimes referred to as “component (B)”) which generates acid uponexposure, the base component (A) including a polymeric compound (A1)containing 0 to 20 mol % of a structural unit (a3) containing a polargroup-containing aliphatic hydrocarbon group, and the acid generatorcomponent (B) containing an acid generator (B1) consisting of a compoundrepresented by general formula (b1-1) shown below.

When a resist film is formed using the resist composition and the formedresist film is subjected to a selective exposure, acid is generated atexposed portions, and the generated acid acts on the component (A) tochange the solubility of the component (A) in a developing solution,whereas the solubility of the component (A) in a developing solution isnot changed at unexposed portions, thereby generating difference insolubility in a developing solution between exposed portions andunexposed portions. Therefore, by subjecting the resist film todevelopment, the exposed portions are dissolved and removed to form apositive-tone resist pattern in the case of a positive resist, whereasthe unexposed portions are dissolved and removed to form a negative-toneresist pattern in the case of a negative resist.

In the present specification, a resist composition which forms apositive resist pattern by dissolving and removing the exposed portionsis called a positive resist composition, and a resist composition whichforms a negative resist pattern by dissolving and removing the unexposedportions is called a negative resist composition.

In the present embodiment, the resist composition may be either apositive resist composition or a negative resist composition.

Further, in the present embodiment, the resist composition may beapplied to an alkali developing process using an alkali developingsolution in the developing treatment, or a solvent developing processusing a developing solution containing an organic solvent (organicdeveloping solution) in the developing treatment, and preferably asolvent developing process.

<Component (A)>

In the present invention, the term “base component” refers to an organiccompound capable of forming a film, and is preferably an organiccompound having a molecular weight of 500 or more. When the organiccompound has a molecular weight of 500 or more, the film-forming abilityis improved, and a photosensitive resin pattern of nano level can beeasily formed.

The organic compound used as the base component is broadly classifiedinto non-polymers and polymers.

In general, as a non-polymer, any of those which have a molecular weightin the range of 500 to less than 4,000 is used. Hereafter, a “lowmolecular weight compound” refers to a non-polymer having a molecularweight in the range of 500 to less than 4,000.

As a polymer, any of those which have a molecular weight of 1,000 ormore is generally used. Hereafter, a “resin” refers to a polymer havinga molecular weight of 1,000 or more.

As the molecular weight of the polymer, the weight average molecularweight in terms of the polystyrene equivalent value determined by gelpermeation chromatography (GPC) is used.

As the component (A′), a resin, a low molecular weight compound, or acombination thereof may be used.

The component (A) may be a resin that exhibits increased solubility in adeveloping solution under action of acid or a resin that exhibitsdecreased solubility in a developing solution under action of acid.

In the present invention, the component (A) may be a component thatgenerates acid upon exposure.

In the present invention, the component (A) includes a polymericcompound (A1) (hereafter, referred to as “component (A1)”) including 0to 20 mol % of a structural unit (a3) containing a polargroup-containing aliphatic hydrocarbon group.

Also, the component (A1) may further include, in addition to thestructural unit (a3), at least one structural unit selected from thegroup consisting of structural units (a1), (a2) and (a4) describedlater, and preferably further include a structural unit (a2).

(Structural Unit (a3))

The structural unit (a3) is a structural unit containing a polargroup-containing aliphatic hydrocarbon group (provided that thestructural units that fall under the definition of structural units (a1)and (a2) described later are excluded).

When the component (A1) includes the structural unit (a3), it ispresumed that the hydrophilicity of the component (A1) is enhanced,thereby contributing to improvement in resolution.

Examples of the polar group include a hydroxyl group, cyano group,carboxyl group, or hydroxyalkyl group in which part of the hydrogenatoms of the alkyl group have been substituted with fluorine atoms,although a hydroxyl group is particularly desirable.

Examples of the aliphatic hydrocarbon group include linear or branchedhydrocarbon groups (preferably alkylene groups) of 1 to 10 carbon atoms,and cyclic aliphatic hydrocarbon groups (cyclic groups). These cyclicgroups can be selected appropriately from the multitude of groups thathave been proposed for the resins of resist compositions designed foruse with ArF excimer lasers. The cyclic group is preferably a polycyclicgroup, more preferably a polycyclic group of 7 to 30 carbon atoms.

Of the various possibilities, structural units derived from an acrylateester that include an aliphatic polycyclic group that contains ahydroxyl group, cyano group, carboxyl group or a hydroxyalkyl group inwhich part of the hydrogen atoms of the alkyl group have beensubstituted with fluorine atoms are particularly desirable. Examples ofthe polycyclic group include groups in which two or more hydrogen atomshave been removed from a bicycloalkane, tricycloalkane, tetracycloalkaneor the like. Specific examples include groups in which two or morehydrogen atoms have been removed from a polycycloalkane such asadamantane, norbornane, isobornane, tricyclodecane ortetracyclododecane. Of these polycyclic groups, groups in which two ormore hydrogen atoms have been removed from adamantane, norbornane ortetracyclododecane are preferred industrially.

As the structural unit (a3), there is no particular limitation as longas it is a structural unit containing a polar group-containing aliphatichydrocarbon group, and an arbitrary structural unit may be used.

The structural unit (a3) is preferably a structural unit derived from anacrylate ester which may have the hydrogen atom bonded to the carbonatom on the α-position substituted with a substituent and contains apolar group-containing aliphatic hydrocarbon group.

When the aliphatic hydrocarbon group within the polar group-containingaliphatic hydrocarbon group is a linear or branched hydrocarbon group of1 to 10 carbon atoms, the structural unit (a3) is preferably astructural unit derived from a hydroxyethyl ester of acrylic acid. Onthe other hand, when the hydrocarbon group is a polycyclic group,structural units represented by formulas (a3-1), (a3-2) and (a3-3) shownbelow are preferable.

In the formulas, R is the same as defined above; j is an integer of 1 to3; k is an integer of 1 to 3; t′ is an integer of 1 to 3; l is aninteger of 1 to 5; and s is an integer of 1 to 3.

In formula (a3-1), j is preferably 1 or 2, and more preferably 1. When jis 2, it is preferable that the hydroxyl groups be bonded to the 3rd and5th positions of the adamantyl group. When j is 1, it is preferable thatthe hydroxyl group be bonded to the 3rd position of the adamantyl group.

j is preferably 1, and it is particularly desirable that the hydroxylgroup be bonded to the 3rd position of the adamantyl group.

In formula (a3-2), k is preferably 1. The cyano group is preferablybonded to the 5th or 6th position of the norbornyl group.

In formula (a3-3), t′ is preferably 1. l is preferably 1. s ispreferably 1. Further, it is preferable that a 2-norbornyl group or3-norbornyl group be bonded to the terminal of the carboxy group of theacrylic acid. The fluorinated alkyl alcohol is preferably bonded to the5th or 6th position of the norbornyl group.

As the structural unit (a3) contained in the component (A), 1 kind ofstructural unit may be used, or 2 or more kinds may be used.

In the component (A1), the amount of the structural unit (a3) based onthe combined total of all structural units constituting the component(A1) is 0 to 20 mol %, preferably 0 to 15 mol %, more preferably 0 to 10mol %, and still more preferably 0 to 5 mol %.

When the amount of the structural unit (a3) is at least as large as thelower limit of the above-mentioned range, the effect of using thestructural unit (a3) can be satisfactorily achieved. On the other hand,when the amount of the structural unit (a3) is no more than the upperlimit of the above-mentioned range, various lithography properties suchas resolution, EL margin and CDU are improved. Further, a good balancecan also be reliably achieved with the other structural units.

(Structural Unit (a1))

The structural unit (a1) is a structural unit containing an aciddecomposable group that exhibits increased polarity by the action ofacid.

The term “acid decomposable group” refers to a group in which at least apart of the bond within the structure thereof is cleaved by the actionof an acid.

Examples of acid decomposable groups which exhibit increased polarity bythe action of an acid include groups which are decomposed by the actionof an acid to form a polar group.

Examples of the polar group include a carboxy group, a hydroxy group, anamino group and a sulfo group (—SO₃H). Among these, a polar groupcontaining —OH in the structure thereof (hereafter, referred to as“OH-containing polar group”) is preferable, a carboxy group or a hydroxygroup is more preferable, and a carboxy group is particularly desirable.

More specifically, as an example of an acid decomposable group, a groupin which the aforementioned polar group has been protected with an aciddissociable group (such as a group in which the hydrogen atom of theOH-containing polar group has been protected with an acid dissociablegroup) can be given.

The “acid dissociable group” refers to both (i) a group in which thebond between the acid dissociable group and the adjacent atom is cleavedby the action of acid; and (ii) a group in which one of the bonds iscleaved by the action of acid, and then a decarboxylation reactionoccurs, thereby cleaving the bond between the acid dissociable group andthe adjacent atom.

It is necessary that the acid dissociable group that constitutes theacid decomposable group is a group which exhibits a lower polarity thanthe polar group generated by the dissociation of the acid dissociablegroup. Thus, when the acid dissociable group is dissociated by theaction of acid, a polar group exhibiting a higher polarity than that ofthe acid dissociable group is generated, thereby increasing thepolarity. As a result, the polarity of the entire component (A1) isincreased. By the increase in the polarity, the solubility in an alkalideveloping solution changes, and the solubility in an alkali developingsolution is relatively increased, whereas the solubility in an organicdeveloping solution is relatively decreased.

Examples of the acid dissociable group include groups which have beenproposed as acid dissociable groups for the base resin of a conventionalchemically amplified resist composition.

Specific examples of acid dissociable groups for the base resin of aconventional chemically amplified resist composition include“acetal-type acid dissociable group”, “tertiary alkyl ester-type aciddissociable group” and “tertiary alkyloxycarbonyl acid dissociablegroup” described below.

Acetal-Type Acid Dissociable Group

Examples of the acid dissociable group for protecting the carboxy groupor hydroxy group as a polar group include the acid dissociable grouprepresented by general formula (a1-r-1) shown below (hereafter, referredto as “acetal-type acid dissociable group”).

In the formula, Ra′¹ and Ra′² represents a hydrogen atom or an alkylgroup; and Ra′³ represents a hydrocarbon group, provided that Ra′³ maybe bonded to Ra′¹ or Ra′².

In the formula (a1-r-1), it is preferable that at least one of Ra′¹ andRa′² represents a hydrogen atom, and it is more preferable that both ofRa′¹ and Ra′² represent a hydrogen atom.

In the case where Ra′¹ or Ra′² is an alkyl group, as the alkyl group,the same alkyl groups as those described above the for the substituentwhich may be bonded to the carbon atom on the α-position of theaforementioned α-substituted acrylate ester can be mentioned, and analkyl group of 1 to 5 carbon atoms is preferable. Specific examplesinclude linear or branched alkyl groups. Specific examples of the alkylgroup include a methyl group, an ethyl group, a propyl group, anisopropyl group, an n-butyl group, an isobutyl group, a tert-butylgroup, a pentyl group, an isopentyl group and a neopentyl group. Ofthese, a methyl group or an ethyl group is preferable, and a methylgroup is particularly preferable.

In formula (a1-r-1), examples of the hydrocarbon group for Ra′³ includea linear or branched alkyl group and a cyclic hydrocarbon group.

The linear alkyl group preferably has 1 to 5 carbon atoms, morepreferably 1 to 4, and still more preferably 1 or 2. Specific examplesinclude a methyl group, an ethyl group, an n-propyl group, an n-butylgroup and an n-pentyl group. Among these, a methyl group, an ethyl groupor an n-butyl group is preferable, and a methyl group or an ethyl groupis more preferable.

The branched alkyl group preferably has 3 to 10 carbon atoms, and morepreferably 3 to 5. Specific examples include an isopropyl group, anisobutyl group, a tert-butyl group, an isopentyl group, a neopentylgroup a 1,1-diethylpropyl group and a 2,2-dimethylbutyl group. Amongthese, an isopropyl group is preferable.

In the case where Ra′³ represents a cyclic hydrocarbon group, the cyclichydrocarbon group may be an aliphatic hydrocarbon group or an aromatichydrocarbon group, and may be polycyclic or monocyclic.

As the monocyclic aliphatic hydrocarbon group, a group in which 1hydrogen atom has been removed from a monocycloalkane is preferable. Themonocycloalkane preferably has 3 to 6 carbon atoms, and specificexamples thereof include cyclopentane and cyclohexane.

As the polycyclic aliphatic hydrocarbon group, a group in which 1hydrogen atom has been removed from a polycycloalkane is preferable, andthe polycyclic group preferably has 7 to 12 carbon atoms. Examples ofthe polycycloalkane include adamantane, norbornane, isobornane,tricyclodecane and tetracyclododecane.

When the monovalent hydrocarbon group for Ra′³ is an aromatichydrocarbon group, the aromatic hydrocarbon group is a hydrocarbon grouphaving at least one aromatic ring.

The aromatic ring is not particularly limited, as long as it is a cyclicconjugated compound having (4n+2)π electrons, and may be eithermonocyclic or polycyclic. The aromatic ring preferably has 5 to 30carbon atoms, more preferably 5 to 20, still more preferably 6 to 15,and most preferably 6 to 12.

Examples of the aromatic ring include aromatic hydrocarbon rings, suchas benzene, naphthalene, anthracene and phenanthrene; and aromatichetero rings in which part of the carbon atoms constituting theaforementioned aromatic hydrocarbon rings has been substituted with ahetero atom. Examples of the hetero atom within the aromatic heterorings include an oxygen atom, a sulfur atom and a nitrogen atom.Specific examples of the aromatic hetero ring include a pyridine ringand a thiophene ring.

Specific examples of the aromatic hydrocarbon group for Ra′³ include agroup in which one hydrogen atom has been removed from theaforementioned aromatic hydrocarbon ring or aromatic hetero ring (arylgroup or heteroaryl group); a group in which one hydrogen atom has beenremoved from an aromatic compound having two or more aromatic rings(biphenyl, fluorene or the like); and a group in which one hydrogen atomof the aforementioned aromatic hydrocarbon ring or aromatic hetero ringhas been substituted with an alkylene group (an arylalkyl group such asa benzyl group, a phenethyl group, a 1-naphthylmethyl group, a2-naphthylmethyl group, a 1-naphthylethyl group, or a 2-naphthylethylgroup). The alkylene group bonded to the aforementioned aromatichydrocarbon ring or the aromatic hetero ring preferably has 1 to 4carbon atoms, more preferably 1 or 2 carbon atoms, and most preferably 1carbon atom.

The cyclic hydrocarbon group for Ra′³ may have a substituent. Examplesof the substituent include —R^(P1), —R^(P2)—O—R^(P1), —R^(P2)—CO—R^(P1),—R^(P2)—CO—OR^(P1), —R^(P2)—O—CO—R^(P1), —R^(P2)—OH, —R^(P2)—CN or—R^(P2)—COOH (hereafter, these substituents are sometimes collectivelyreferred to as “Ra⁰⁵”).

Here, R^(P1) is a monovalent chain saturated hydrocarbon group having 1to 10 carbon atoms, a monovalent aliphatic cyclic saturated hydrocarbongroup having 3 to 20 carbon atoms, or a monovalent aromatic hydrocarbongroup having 6 to 30 carbon atoms. Further, R^(P2) is a single bond, adivalent chain saturated hydrocarbon group having 1 to 10 carbon atoms,a divalent aliphatic cyclic saturated hydrocarbon group having 3 to 20carbon atoms, or a divalent aromatic hydrocarbon group having 6 to 30carbon atoms.

Here, a portion or all of the hydrogen atoms having the chain saturatedhydrocarbon group, the aliphatic cyclic saturated hydrocarbon group, andthe aromatic hydrocarbon group for R^(P1) and R^(P2) may be substitutedwith a fluorine atom. The aliphatic cyclic hydrocarbon group may have 1or more substituents of 1 kind, or 1 or more substituents of a pluralityof kinds.

Examples of the monovalent chain saturated hydrocarbon group having 1 to10 carbon atoms include a methyl group, an ethyl group, a propyl group,a butyl group, a pentyl group, a hexyl group, a heptyl group, an octylgroup, and a decyl group.

Examples of the monovalent aliphatic cyclic saturated hydrocarbon grouphaving 3 to 20 carbon atoms include a monocyclic aliphatic saturatedhydrocarbon group such as a cyclopropyl group, a cyclobutyl group, acyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctylgroup, a cyclodecyl group, and a cyclododecyl group; and a polycyclicaliphatic saturated hydrocarbon group such as a bicyclo[2.2.2]octanylgroup, a tricyclo[5.2.1.02,6]decanyl group, atricyclo[3.3.1.13,7]decanyl group, atetracyclo[6.2.1.13,6.02,7]dodecanyl group, and an adamantyl group.

Examples of the monovalent aromatic hydrocarbon group having 6 to 30carbon atoms include a group obtained by removing one hydrogen atom fromthe aromatic hydrocarbon ring such as benzene, biphenyl, fluorene,naphthalene, anthracene, and phenanthrene.

In the case where Ra′³ is bonded to Ra′¹ or Ra′² to form a ring, thecyclic group is preferably a 4 to 7-membered ring, and more preferably a4 to 6-membered ring. Specific examples of the cyclic group includetetrahydropyranyl group and tetrahydrofuranyl group.

Tertiary Alkyl Ester-Type Acid Dissociable Group

Examples of the acid dissociable group for protecting the carboxy groupas a polar group include the acid dissociable group represented bygeneral formula (a1-r-2) shown below.

Among the acid dissociable groups represented by general formula(a1-r-2), for convenience, a group which is constituted of alkyl groupsis referred to as “tertiary ester-type acid dissociable group”.

In the formula, Ra′⁴ to Ra′⁶ each independently represents a hydrocarbongroup, provided that Ra′⁵ and Ra′⁶ may be mutually bonded to form aring.

Examples of the hydrocarbon group for Ra′⁴ include a linear or branchedalkyl group, a chain or cyclic alkenyl group, and a cyclic hydrocarbongroup.

The linear or branched alkyl group and the cyclic hydrocarbon group(monocyclic aliphatic hydrocarbon group, polycyclic aliphatichydrocarbon group or aromatic hydrocarbon group) for Ra′⁴ are the sameas defined for Ra′³.

The chain or cyclic alkenyl group for Ra′⁴ is preferably an alkenylgroup having 2 to 10 carbon atoms.

The hydrocarbon group for Ra′⁵ and Ra′⁶ is the same as defined for Ra′³.

In the case where Ra′⁵ and Ra′⁶ are mutually bonded to form a ring, agroup represented by general formula (a1-r2-1) shown below, a grouprepresented by general formula (a1-r2-2) shown below, and a grouprepresented by general formula (a1-r2-3) shown below may be given aspreferable examples.

On the other hand, in the case where Ra′⁴ to Ra′⁶ are not mutuallybonded and independently represent a hydrocarbon group, the grouprepresented by general formula (a1-r2-4) shown below may be given as apreferable example.

In formula (a1-r2-1), Ra′¹⁰ represents an alkyl group of 1 to 10 carbonatoms; Ra′¹¹ is a group which forms an aliphatic cyclic group togetherwith a carbon atom having Ra′¹⁰ bonded thereto. In formula (a1-r2-2), Yarepresents a carbon atom; Xa represents a group which forms a cyclichydrocarbon group together with Ya, provided that part or all of thehydrogen atoms of the cyclic hydrocarbon group may be substituted;

Ra⁰¹ to Ra⁰³ each independently represents a hydrogen atom, a monovalentsaturated chain hydrocarbon group of 1 to 10 carbon atoms or amonovalent saturated aliphatic cyclic hydrocarbon group of 3 to 20carbon atoms, provided that part or all of the hydrogen atoms of thesaturated chain hydrocarbon or the saturated aliphatic cyclichydrocarbon may be substituted; two or more of Ra⁰¹ to Ra⁰³ may bemutually bonded to form a cyclic structure; and * represents a valencebond. In formula (a1-r2-3), Yaa represents a carbon atom; Xaa representsa group which forms an aliphatic cyclic group together with Yaa; Ra⁰⁴represents an aromatic hydrocarbon group which may have a substituent;and * represents a valence bond. In formula (a1-r2-4), Ra′¹² and Ra′¹³each independently represents a hydrogen atom or a monovalent saturatedhydrocarbon group of 1 to 10 carbon atoms, provided that part or all ofthe hydrogen atoms of the saturated hydrocarbon group may besubstituted; Ra′¹⁴ represents an aromatic hydrocarbon group which mayhave a substituent; and * represents a valence bond (the same definitionhereafter).

In the formula (a1-r2-1), as the alkyl group of 1 to 10 carbon atoms forRa′¹⁰, the same groups as described above for the linear or branchedalkyl group for Ra′³ in the formula (a1-r-1) are preferable.

Ra′¹⁰ is preferably an alkyl group of 1 to 5 carbon atoms.

In formula (a1-r2-1), the aliphatic cyclic group which is formed byRa′¹¹ together with the carbon atom bonded to Ra′¹⁰, the same groups asthose described above for the monocyclic or polycyclic aliphatichydrocarbon group for Ra′³ in formula (a1-r-1) are preferable.

In formula (a1-r2-2), as the cyclic hydrocarbon group formed by Xatogether with Ya, a group in which 1 or more hydrogen atoms have beenremoved from the monovalent cyclic hydrocarbon group (aliphatichydrocarbon group or aromatic hydrocarbon group) for Ra′³ in theaforementioned formula (a1-r-1) may be mentioned.

The cyclic hydrocarbon group which Xa forms with Ya may have asubstituent. Examples of substituents include the same substituents asthose which the cyclic hydrocarbon group for Ra′³ may have.

In formula (a1-r2-2), examples of the monovalent saturated chainhydrocarbon group of 1 to 10 carbon atoms for Ra⁰¹ to Ra⁰³ include amethyl group, an ethyl group, a propyl group, a butyl group, a pentylgroup, a hexyl group, a heptyl group, an octyl group, and a decyl group.

Examples of the monovalent aliphatic cyclic saturated hydrocarbon grouphaving 3 to 20 carbon atoms for Ra⁰¹ to Ra⁰³ include a monocyclicaliphatic saturated hydrocarbon group such as a cyclopropyl group, acyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptylgroup, a cyclooctyl group, a cyclodecyl group, and a cyclododecyl group;and a polycyclic aliphatic saturated hydrocarbon group such as abicyclo[2.2.2]octanyl group, a tricyclo[5.2.1.02,6]decanyl group, atricyclo[3.3.1.13,7]decanyl group, atetracyclo[6.2.1.13,6.02,7]dodecanyl group, and an adamantyl group.

Among these examples, as Ra⁰¹ to Ra⁰³, in terms of ease in synthesis ofthe monomeric compound which derives the structural unit (a1), ahydrogen atom or a saturated chain hydrocarbon group having 1 to 10carbon atoms is preferable, a hydrogen atom, a methyl group or an ethylgroup is more preferable, and a hydrogen atom is most preferable.

As the substituent for the saturated chain hydrocarbon group orsaturated cyclic aliphatic hydrocarbon group represented by Ra⁰¹ toRa⁰³, for example, the same substituents as those described above forRa⁰⁵ may be mentioned.

Examples of the group containing a carbon-carbon double bond which isgenerated by forming a cyclic structure in which two or more of Ra⁰¹ toRa⁰³ are bonded to each other include a cyclopentenyl group, acyclohexenyl group, a methyl cyclopentenyl group, a methyl cyclohexenylgroup, a cyclopentylideneethenyl group, and a cyclohexylidenethenylgroup. Among these examples, from the viewpoint of the ease of synthesisof the monomer compound which derives the structural unit (a1), acyclopentenyl group, a cyclohexenyl group, and a cyclopentylidenethenylgroup are preferable.

In formula (a1-r2-3), an aliphatic cyclic group which is formed of Xaatogether with Yaa is preferably a group exemplified as an aliphatichydrocarbon group which is a monocyclic group or a polycyclic group ofRa′³ in general formula (a1-r-1).

In general formula (a1-r2-3), examples of the aromatic hydrocarbon groupfor Ra⁰⁴ include a group obtained by removing one or more hydrogen atomsfrom an aromatic hydrocarbon ring having 5 to 30 carbon atoms. Amongthese examples, Ra⁰⁴ is preferably a group obtained by removing one ormore hydrogen atoms from an aromatic hydrocarbon ring having 6 to 15carbon atoms, a group obtained by removing one or more hydrogen atomsfrom benzene, naphthalene, anthracene, or phenanthrene is furtherpreferable, a group obtained by removing one or more hydrogen atoms frombenzene, naphthalene, or anthracene is still further preferable, a groupobtained by removing one or more hydrogen atoms from benzene andnaphthalene is particularly preferable, and a group obtained by removingone or more hydrogen atoms from benzene is most preferable.

Examples of the substituent that Ra⁰⁴ in general formula (a1-r2-3) mayhave include a methyl group, an ethyl group, a propyl group, a hydroxylgroup, a carboxyl group, a halogen atom (a fluorine atom, a chlorineatom, a bromine atom, or the like), an alkoxy group (a methoxy group, anethoxy group, a propoxy group, a butoxy group, or the like), and analkyloxycarbonyl group.

In general formula (a1-r2-4), Ra′¹² and Ra′¹³ each independentlyrepresent a monovalent chain saturated hydrocarbon group having 1 to 10carbon atoms or a hydrogen atom. With respect to Ra′¹² and Ra′¹³,examples of the monovalent chain saturated hydrocarbon group having 1 to10 carbon atoms include the same monovalent chain saturated hydrocarbongroup having 1 to 10 carbon atoms as that for Ra⁰¹ to Ra⁰³, providedthat part or all of the hydrogen atoms of the saturated hydrocarbongroup may be substituted;

Among these examples, as Ra′¹² and Ra′¹³, a hydrogen atom and an alkylgroup having 1 to 5 carbon atoms are preferable, an alkyl group having 1to 5 carbon atoms is further preferable, a methyl group and an ethylgroup are still further preferable, and a methyl group is particularlypreferable.

In the case where the chain saturated hydrocarbon group represented byRa′¹² and Ra′¹³ is substituted, examples of the substituent include thesame group as that of Ra⁰⁵.

In general formula (a1-r2-4), Ra′¹⁴ is an aromatic hydrocarbon groupwhich may have a substituent. Examples of the hydrocarbon group forRa′¹⁴ include the same aromatic hydrocarbon groups as those exemplifiedin the description for Ra⁰⁴. Among these examples, Ra′¹⁴ is preferably agroup obtained by removing one or more hydrogen atoms from the aromatichydrocarbon group having 6 to 15 carbon atoms, is further preferably agroup obtained by removing one or more hydrogen atoms from benzene,naphthalene, anthracene, or phenanthrene, is still further preferably agroup obtained by removing one or more hydrogen atoms from benzene,naphthalene, or anthracene, is particularly preferably a group obtainedby removing one or more hydrogen atoms from naphthalene or anthracene,and is most preferably a group obtained by removing one or more hydrogenatoms from naphthalene.

Examples of the substituent that Ra′¹⁴ may have include the same groupas the substituent that Ra⁰⁴ may have.

In the case where Ra′¹⁴ in general formula (a1-r2-4) is a naphthylgroup, a position which is bonded to a tertiary carbon atom in generalformula (a1-r2-4) may be 1-position and 2-position of the naphthylgroup.

In the case where Ra′¹⁴ in general formula (a1-r2-4) is an anthrylgroup, a position which is bonded to a tertiary carbon atom in generalformula (a1-r2-4) may be any one of 1-position, 2-position, and9-position of the anthryl group.

Specific examples of the group represented by the aforementioned formula(a1-r2-1) are shown below.

Specific examples of the group represented by the aforementioned formula(a1-r2-2) are shown below.

Specific examples of the group represented by the aforementioned formula(a1-r2-3) are shown below.

Specific examples of the group represented by the aforementioned formula(a1-r2-4) are shown below.

Tertiary Alkyloxycarbonyl Acid Dissociable Group

Examples of the acid dissociable group for protecting a hydroxy group asa polar group include the acid dissociable group represented by generalformula (a1-r-3) shown below (hereafter, for convenience, referred to as“tertiary alkyloxycarbonyl-type acid dissociable group”).

In the formula, Ra′⁷ to Ra′⁹ each independently represents an alkylgroup.

In the formula (a1-r-3), Ra′⁷ to Ra′⁹ is preferably an alkyl group of 1to 5 carbon atoms, and more preferably an alkyl group of 1 to 3 carbonatoms.

Further, the total number of carbon atoms within the alkyl group ispreferably 3 to 7, more preferably 3 to 5, and most preferably 3 or 4.

Examples of the structural unit (a1) include a structural unit derivedfrom an acrylate ester which may have the hydrogen atom bonded to thecarbon atom on the α-position substituted with a substituent; astructural unit derived from an acrylamide; a structural unit derivedfrom hydroxystyrene or a hydroxystyrene derivative in which at least apart of the hydrogen atom of the hydroxy group is protected with asubstituent containing an acid decomposable group; and a structural unitderived from vinylbenzoic acid or a vinylbenzoic acid derivative inwhich at least a part of the hydrogen atom within —C(═O)—OH is protectedwith a substituent containing an acid decomposable group.

As the structural unit (a1), a structural unit derived from an acrylateester which may have the hydrogen atom bonded to the carbon atom on theα-position substituted with a substituent is preferable.

Specific examples of preferable structural units for the structural unit(a1) include structural units represented by general formula (a1-1) or(a1-2) shown below.

In the formula, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; Va¹represents a divalent hydrocarbon group optionally having an ether bond;n_(a1) represents an integer of 0 to 2; Ra¹ represents an aciddissociable group represented by the aforementioned formula (a1-r-1) or(a1-r-2); Wa¹ represents a hydrocarbon group having a valency ofn_(a2)+1; n_(a2) represents an integer of 1 to 3; and Ra² represents anacid dissociable group represented by the aforementioned formula(a1-r-1) or (a1-r-3).

In the aforementioned formula (a1-1), as the alkyl group of 1 to 5carbon atoms for R, a linear or branched alkyl group of 1 to 5 carbonatoms is preferable, and specific examples thereof include a methylgroup, an ethyl group, a propyl group, an isopropyl group, an n-butylgroup, an isobutyl group, a tert-butyl group, a pentyl group, anisopentyl group and a neopentyl group. The halogenated alkyl group of 1to 5 carbon atoms represented by R is a group in which part or all ofthe hydrogen atoms of the aforementioned alkyl group of 1 to 5 carbonatoms have been substituted with halogen atoms. Examples of the halogenatom include a fluorine atom, a chlorine atom, a bromine atom and aniodine atom, and a fluorine atom is particularly desirable.

As R, a hydrogen atom, an alkyl group of 1 to 5 carbon atoms or afluorinated alkyl group of 1 to 5 carbon atoms is preferable, and ahydrogen atom or a methyl group is particularly desirable in terms ofindustrial availability.

In formula (a1-1), the divalent hydrocarbon group for V¹ may be eitheran aliphatic hydrocarbon group or an aromatic hydrocarbon group.

The aliphatic hydrocarbon group as the divalent hydrocarbon group forVa¹ may be either saturated or unsaturated. In general, the aliphatichydrocarbon group is preferably saturated.

As specific examples of the aliphatic hydrocarbon group, a linear orbranched aliphatic hydrocarbon group, and an aliphatic hydrocarbon groupcontaining a ring in the structure thereof can be given.

The linear aliphatic hydrocarbon group preferably has 1 to 10 carbonatoms, more preferably 1 to 6, still more preferably 1 to 4, and mostpreferably 1 to 3.

As the linear aliphatic hydrocarbon group, a linear alkylene group ispreferable. Specific examples thereof include a methylene group [—CH₂—],an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], atetramethylene group [—(CH₂)₄-] and a pentamethylene group [—(CH₂)₅—].

The branched aliphatic hydrocarbon group preferably has 3 to 10 carbonatoms, more preferably 3 to 6 carbon atoms, still more preferably 3 or 4carbon atoms, and most preferably 3 carbon atoms.

As the branched aliphatic hydrocarbon group, branched alkylene groupsare preferred, and specific examples include various alkylalkylenegroups, including alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—,—C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and —C(CH₂CH₃)₂—;alkylethylene groups such as —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—,—C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—; alkyltrimethylenegroups such as —CH(CH₃)CH₂CH₂—, and —CH₂CH(CH₃)CH₂—; andalkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—, and—CH₂CH(CH₃)CH₂CH₂—. As the alkyl group within the alkylalkylene group, alinear alkyl group of 1 to 5 carbon atoms is preferable.

As examples of the hydrocarbon group containing a ring in the structurethereof, an alicyclic hydrocarbon group (a group in which two hydrogenatoms have been removed from an aliphatic hydrocarbon ring), a group inwhich the alicyclic hydrocarbon group is bonded to the terminal of theaforementioned chain-like aliphatic hydrocarbon group, and a group inwhich the alicyclic group is interposed within the aforementioned linearor branched aliphatic hydrocarbon group, can be given. The linear orbranched aliphatic hydrocarbon group is the same as defined for theaforementioned linear aliphatic hydrocarbon group or the aforementionedbranched aliphatic hydrocarbon group.

The alicyclic hydrocarbon group preferably has 3 to 20 carbon atoms, andmore preferably 3 to 12 carbon atoms.

The alicyclic hydrocarbon group may be either a monocyclic group or apolycyclic group. As the monocyclic aliphatic hydrocarbon group, a groupin which 2 hydrogen atoms have been removed from a monocycloalkane ispreferable. The monocycloalkane preferably has 3 to 6 carbon atoms, andspecific examples thereof include cyclopentane and cyclohexane. As thepolycyclic group, a group in which two hydrogen atoms have been removedfrom a polycycloalkane is preferable, and the polycyclic grouppreferably has 7 to 12 carbon atoms. Examples of the polycycloalkaneinclude adamantane, norbornane, isobornane, tricyclodecane andtetracyclododecane.

The aromatic hydrocarbon group as the divalent hydrocarbon group for Va¹is a hydrocarbon group having an aromatic ring.

The aromatic hydrocarbon group preferably has 3 to 30 carbon atoms, morepreferably 5 to 30, still more preferably 5 to 20, still more preferably6 to 15, and most preferably 6 to 10. Here, the number of carbon atomswithin a substituent(s) is not included in the number of carbon atoms ofthe aromatic hydrocarbon group.

Examples of the aromatic ring contained in the aromatic hydrocarbongroup include aromatic hydrocarbon rings, such as benzene, biphenyl,fluorene, naphthalene, anthracene and phenanthrene; and aromatic heterorings in which part of the carbon atoms constituting the aforementionedaromatic hydrocarbon rings has been substituted with a hetero atom.Examples of the hetero atom within the aromatic hetero rings include anoxygen atom, a sulfur atom and a nitrogen atom.

Specific examples of the aromatic hydrocarbon group include a group inwhich two hydrogen atoms have been removed from the aforementionedaromatic hydrocarbon ring (arylene group); and a group in which onehydrogen atom has been removed from the aforementioned aromatichydrocarbon ring (aryl group) and one hydrogen atom has been substitutedwith an alkylene group (such as a benzyl group, a phenethyl group, a1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethylgroup, or a 2-naphthylethyl group). The alkylene group (alkyl chainwithin the arylalkyl group) preferably has 1 to 4 carbon atom, morepreferably 1 or 2, and most preferably 1.

In formula (a1-1), Ra¹ represents an acid dissociable group representedby the aforementioned formula (a1-r-1) or (a1-r-2).

In the aforementioned formula (a1-2), the hydrocarbon group for Wa¹having a valency of n_(a2)+1 may be either an aliphatic hydrocarbongroup or an aromatic hydrocarbon group. The aliphatic cyclic grouprefers to a hydrocarbon group that has no aromaticity, and may be eithersaturated or unsaturated, but is preferably saturated. Examples of thealiphatic hydrocarbon group include a linear or branched aliphatichydrocarbon group, an aliphatic hydrocarbon group containing a ring inthe structure thereof, and a combination of the linear or branchedaliphatic hydrocarbon group and the aliphatic hydrocarbon groupcontaining a ring in the structure thereof.

The valency of n_(a2)+1 is preferably divalent, trivalent ortetravalent, and divalent or trivalent is more preferable.

Specific examples of structural unit represented by formula (a1-1) areshown below. In the formulae shown below, R^(α) represents a hydrogenatom, a methyl group or a trifluoromethyl group.

Specific examples of structural unit represented by formula (a1-2) areshown below.

As the structural unit (a1) contained in the component (A1), 1 type ofstructural unit may be used, or 2 or more types may be used.

In the component (A1), the amount of the structural unit (a1) based onthe combined total of all structural units constituting the component(A1) is preferably 10 to 80 mol %, more preferably 20 to 70 mol %, andstill more preferably 30 to 65 mol %.

When the amount of the structural unit (a1) is at least as large as thelower limit of the above-mentioned range, a resist pattern can bereliably obtained, and various lithography properties such as resolutionand roughness are further improved. On the other hand, when the amountof the structural unit (a1) is no more than the upper limit of theabove-mentioned range, a good balance can be achieved with the otherstructural units.

(Structural Unit (a2))

The component (A1) may further include a structural unit (a2) whichcontains a lactone-containing cyclic group, an —SO₂— containing cyclicgroup or a carbonate-containing cyclic group (provided that structuralunits which fall under the definition of the structural unit (a1) areexcluded).

When the component (A1) is used for forming a resist film, thelactone-containing cyclic group, the —SO₂— containing cyclic group orthe carbonate-containing cyclic group within the structural unit (a2) iseffective in improving the adhesion between the resist film and thesubstrate. Further, by virtue of including the structural unit (a2), inan alkali developing process, during developing, the solubility of theresist film in an alkali developing is enhanced.

The term “lactone-containing cyclic group” refers to a cyclic groupincluding a ring containing a —O—C(═O)— structure (lactone ring). Theterm “lactone ring” refers to a single ring containing a —O—C(O)—structure, and this ring is counted as the first ring. Alactone-containing cyclic group in which the only ring structure is thelactone ring is referred to as a monocyclic group, and groups containingother ring structures are described as polycyclic groups regardless ofthe structure of the other rings. The lactone-containing cyclic groupmay be either a monocyclic group or a polycyclic group.

The lactone-containing cyclic group for the structural unit (a2) is notparticularly limited, and an arbitrary structural unit may be used.Specific examples include groups represented by general formulae(a2-r-1) to (a2-r-7) shown below.

In the formulae, each Ra′²¹ independently represents a hydrogen atom, analkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group,a hydroxy group, —COOR″, —OC(═O)R″, a hydroxyalkyl group or a cyanogroup; R″ represents a hydrogen atom, an alkyl group, alactone-containing cyclic group, a carbonate-containing cyclic group oran —SO₂— containing cyclic group; A″ represents an oxygen atom (—O—), asulfur atom (—S—) or an alkylene group of 1 to 5 carbon atoms which maycontain an oxygen atom or a sulfur atom; n′ represents an integer of 0to 2; and m′ represents 0 or 1.

In formulae (a2-r-1) to (a2-r-7), the alkyl group for Ra′²¹ ispreferably an alkyl group of 1 to 6 carbon atoms. Further, the alkylgroup is preferably a linear alkyl group or a branched alkyl group.Specific examples include a methyl group, an ethyl group, a propylgroup, an isopropyl group, an n-butyl group, an isobutyl group, atert-butyl group, a pentyl group, an isopentyl group, a neopentyl groupand a hexyl group. Among these, a methyl group or ethyl group ispreferable, and a methyl group is particularly desirable.

The alkoxy group for Ra′²¹ is preferably an alkoxy group of 1 to 6carbon atoms.

Further, the alkoxy group is preferably a linear or branched alkoxygroup. Specific examples of the alkoxy groups include the aforementionedalkyl groups for Ra′²¹ having an oxygen atom (—O—) bonded thereto.

As examples of the halogen atom for Ra′²¹, a fluorine atom, chlorineatom, bromine atom and iodine atom can be given. Among these, a fluorineatom is preferable.

Examples of the halogenated alkyl group for Ra′²¹ include groups inwhich part or all of the hydrogen atoms within the aforementioned alkylgroup for Ra′²¹ has been substituted with the aforementioned halogenatoms. As the halogenated alkyl group, a fluorinated alkyl group ispreferable, and a perfluoroalkyl group is particularly desirable.

With respect to —COOR″ and —OC(═O)R″ for Ra′²¹, R″ represents a hydrogenatom, an alkyl group, a lactone-containing cyclic group, acarbonate-containing cyclic group or an —SO₂— containing cyclic group.

The alkyl group for R″ may be linear, branched or cyclic, and preferablyhas 1 to 15 carbon atoms.

When R″ represents a linear or branched alkyl group, it is preferably analkyl group of 1 to 10 carbon atoms, more preferably an alkyl group of 1to 5 carbon atoms, and most preferably a methyl group or an ethyl group.

When R″ is a cyclic alkyl group (cycloalkyl group), it preferably has 3to 15 carbon atoms, more preferably 4 to 12 carbon atoms, and mostpreferably 5 to 10 carbon atoms. Specific examples include groups inwhich one or more hydrogen atoms have been removed from amonocycloalkane or a polycycloalkane such as a bicycloalkane,tricycloalkane or tetracycloalkane which may or may not be substitutedwith a fluorine atom or a fluorinated alkyl group. Specific examplesinclude groups in which one or more hydrogen atoms have been removedfrom a monocycloalkane such as cyclopentane or cyclohexane; and groupsin which one or more hydrogen atoms have been removed from apolycycloalkane such as adamantane, norbornane, isobornane,tricyclodecane or tetracyclododecane.

Examples of the lactone-containing cyclic group for R″ include groupsrepresented by the aforementioned general formulae (a2-r-1) to (a2-r-7).

The carbonate-containing cyclic group for R″ is the same as defined forthe carbonate-containing cyclic group described later. Specific examplesof the carbonate-containing cyclic group include groups represented bygeneral formulae (ax3-r-1) to (ax3-r-3).

The —SO₂— containing cyclic group for R″ is the same as defined for the—SO₂-containing cyclic group described later. Specific examples of the—SO₂— containing cyclic group include groups represented by generalformulae (a5-r-1) to (a5-r-4).

The hydroxyalkyl group for Ra′²¹ preferably has 1 to 6 carbon atoms, andspecific examples thereof include the alkyl groups for Ra′²¹ in which atleast one hydrogen atom has been substituted with a hydroxy group.

In formulae (a2-r-2), (a2-r-3) and (a2-r-5), as the alkylene group of 1to 5 carbon atoms represented by A″, a linear or branched alkylene groupis preferable, and examples thereof include a methylene group, anethylene group, an n-propylene group and an isopropylene group. Examplesof alkylene groups that contain an oxygen atom or a sulfur atom includethe aforementioned alkylene groups in which —O— or —S— is bonded to theterminal of the alkylene group or present between the carbon atoms ofthe alkylene group. Specific examples of such alkylene groups include—O—CH₂—, —CH₂—O—CH₂—, —S—CH₂— and —CH₂—S—CH₂—. As A″, an alkylene groupof 1 to 5 carbon atoms or —O— is preferable, more preferably an alkylenegroup of 1 to 5 carbon atoms, and most preferably a methylene group.

Specific examples of the groups represented by the aforementionedgeneral formulae (a2-r-1) to (a2-r-7) are shown below.

An “—SO₂— containing cyclic group” refers to a cyclic group having aring containing —SO₂— within the ring structure thereof, i.e., a cyclicgroup in which the sulfur atom (S) within —SO₂— forms part of the ringskeleton of the cyclic group. The ring containing —SO₂— within the ringskeleton thereof is counted as the first ring. A cyclic group in whichthe only ring structure is the ring that contains —SO₂— in the ringskeleton thereof is referred to as a monocyclic group, and a groupcontaining other ring structures is described as a polycyclic groupregardless of the structure of the other rings. The —SO₂— containingcyclic group may be either a monocyclic group or a polycyclic group.

As the —SO₂— containing cyclic group, a cyclic group containing —O—SO₂—within the ring skeleton thereof, i.e., a cyclic group containing asultone ring in which —O—S— within the —O—SO₂— group forms part of thering skeleton thereof is particularly desirable.

More specific examples of the —SO₂— containing cyclic group includegroups represented by general formulas (a5-r-1) to (a5-r-4) shown below.

In the formulae, each Ra′⁵¹ independently represents a hydrogen atom, analkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group,a hydroxy group, —COOR″, —OC(═O)R″, a hydroxyalkyl group or a cyanogroup; R″ represents a hydrogen atom, an alkyl group, alactone-containing cyclic group, a carbonate-containing cyclic group oran —SO₂— containing cyclic group; A″ represents an oxygen atom, a sulfuratom or an alkylene group of 1 to 5 carbon atoms which may contain anoxygen atom or a sulfur atom; and n′ represents an integer of 0 to 2.

In general formulae (a5-r-1) and (a5-r-2), A″ is the same as defined forA″ in general formulae (a2-r-2), (a2-r-3) and (a2-r-5).

Examples of the alkyl group, alkoxy group, halogen atom, halogenatedalkyl group, —COOR″, —OC(═O)R″ and hydroxyalkyl group for Ra′⁵¹ includethe same groups as those described above in the explanation of Ra′²¹ inthe general formulas (a2-r-1) to (a2-r-7).

Specific examples of the groups represented by the aforementionedgeneral formulae (a5-r-1) to (a5-r-4) are shown below. In the formulaeshown below, “Ac” represents an acetyl group.

The term “carbonate-containing cyclic group” refers to a cyclic groupincluding a ring containing a —O—C(═O)—O— structure (carbonate ring).The term “carbonate ring” refers to a single ring containing a—O—C(═O)—O— structure, and this ring is counted as the first ring. Acarbonate-containing cyclic group in which the only ring structure isthe carbonate ring is referred to as a monocyclic group, and groupscontaining other ring structures are described as polycyclic groupsregardless of the structure of the other rings. The carbonate-containingcyclic group may be either a monocyclic group or a polycyclic group.

The carbonate-containing cyclic group is not particularly limited, andan arbitrary group may be used. Specific examples include groupsrepresented by general formulae (ax3-r-1) to (ax3-r-3) shown below.

In the formulae, each Ra′^(x31) independently represents a hydrogenatom, an alkyl group, an alkoxy group, a halogen atom, a halogenatedalkyl group, a hydroxy group, —COOR″, —OC(═O)R″, a hydroxyalkyl group ora cyano group; R″ represents a hydrogen atom, an alkyl group, alactone-containing cyclic group, a carbonate-containing cyclic group oran —SO₂— containing cyclic group; A″ represents an oxygen atom, a sulfuratom or an alkylene group of 1 to 5 carbon atoms which may contain anoxygen atom or a sulfur atom; p′ represents an integer of 0 to 3; and q′represents 0 or 1.

In general formulae (ax3-r-2) and (ax3-r-3), A″ is the same as definedfor A″ in general formulae (a2-r-2), (a2-r-3) and (a2-r-5).

Examples of the alkyl group, alkoxy group, halogen atom, halogenatedalkyl group, —COOR″, —OC(═O)R″ and hydroxyalkyl group for Ra′³¹ includethe same groups as those described above in the explanation of Ra′²¹ inthe general formulas (a2-r-1) to (a2-r-7).

Specific examples of the groups represented by the aforementionedgeneral formulae (ax3-r-1) to (ax3-r-3) are shown below.

As the structural unit (a2), a structural unit derived from an acrylateester which may have the hydrogen atom bonded to the carbon atom on theα-position substituted with a substituent is preferable.

The structural unit (a2) is preferably a structural unit represented bygeneral formula (a2-1) shown below.

In the formula, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; Ya²¹represents a single bond or a divalent linking group; La²¹ represents—O—, —COO—, —CON(R′)—, —OCO—, —CONHCO— or —CONHCS—; and R′ represents ahydrogen atom or a methyl group; provided that, when La²¹ represents—O—, Ya²¹ does not represents —CO—; and Ra²¹ represents alactone-containing cyclic group, a carbonate-containing cyclic group oran —SO₂— containing cyclic group.

In the formula (a2-1), R is the same as defined above.

The divalent linking group for Ya²¹ is not particularly limited, andpreferable examples thereof include a divalent hydrocarbon group whichmay have a substituent and a divalent linking group containing a heteroatom.

Divalent Hydrocarbon Group which May have a Substituent:

In the case where Ya²¹ is a divalent linking group which may have asubstituent, the hydrocarbon group may be either an aliphatichydrocarbon group or an aromatic hydrocarbon group.

Aliphatic Hydrocarbon Group for Ya²¹

The “aliphatic hydrocarbon group” refers to a hydrocarbon group that hasno aromaticity. The aliphatic hydrocarbon group may be saturated orunsaturated. In general, the aliphatic hydrocarbon group is preferablysaturated.

Examples of the aliphatic hydrocarbon group include a linear or branchedaliphatic hydrocarbon group, and an aliphatic hydrocarbon groupcontaining a ring in the structure thereof can be given.

Linear or Branched Aliphatic Hydrocarbon Group

The linear aliphatic hydrocarbon group preferably has 1 to 10 carbonatoms, more preferably 1 to 6, still more preferably 1 to 4, and mostpreferably 1 to 3.

As the linear aliphatic hydrocarbon group, a linear alkylene group ispreferable. Specific examples thereof include a methylene group [—CH₂—],an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], atetramethylene group [—(CH₂)₄-] and a pentamethylene group [—(CH₂)₅—].

The branched aliphatic hydrocarbon group preferably has 3 to 10 carbonatoms, more preferably 3 to 6 carbon atoms, still more preferably 3 or 4carbon atoms, and most preferably 3 carbon atoms.

As the branched aliphatic hydrocarbon group, branched alkylene groupsare preferred, and specific examples include various alkylalkylenegroups, including alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—,—C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and —C(CH₂CH₃)₂—;alkylethylene groups such as —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—,—C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—; alkyltrimethylenegroups such as —CH(CH₃)CH₂CH₂—, and —CH₂CH(CH₃)CH₂—; andalkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—, and—CH₂CH(CH₃)CH₂CH₂—. As the alkyl group within the alkylalkylene group, alinear alkyl group of 1 to 5 carbon atoms is preferable.

The linear or branched aliphatic hydrocarbon group may or may not have asubstituent. Examples of the substituent include a fluorine atom, afluorinated alkyl group of 1 to 5 carbon atoms, and a carbonyl group.

Aliphatic Hydrocarbon Group Containing a Ring in the Structure Thereof

As examples of the hydrocarbon group containing a ring in the structurethereof, a cyclic aliphatic hydrocarbon group containing a hetero atomin the ring structure thereof and may have a substituent (a group inwhich two hydrogen atoms have been removed from an aliphatic hydrocarbonring), a group in which the cyclic aliphatic hydrocarbon group is bondedto the terminal of the aforementioned chain-like aliphatic hydrocarbongroup, and a group in which the cyclic aliphatic group is interposedwithin the aforementioned linear or branched aliphatic hydrocarbongroup, can be given. As the linear or branched aliphatic hydrocarbongroup, the same groups as those described above can be used.

The cyclic aliphatic hydrocarbon group preferably has 3 to 20 carbonatoms, and more preferably 3 to 12 carbon atoms.

The cyclic aliphatic hydrocarbon group may be either a polycyclic groupor a monocyclic group. As the monocyclic aliphatic hydrocarbon group, agroup in which 2 hydrogen atoms have been removed from a monocycloalkaneis preferable. The monocycloalkane preferably has 3 to 6 carbon atoms,and specific examples thereof include cyclopentane and cyclohexane. Asthe polycyclic group, a group in which two hydrogen atoms have beenremoved from a polycycloalkane is preferable, and the polycyclic grouppreferably has 7 to 12 carbon atoms. Examples of the polycycloalkaneinclude adamantane, norbornane, isobornane, tricyclodecane andtetracyclododecane.

The cyclic aliphatic hydrocarbon group may or may not have asubstituent. Examples of the substituent include an alkyl group, analkoxy group, a halogen atom, a halogenated alkyl group, a hydroxylgroup and a carbonyl group.

The alkyl group as the substituent is preferably an alkyl group of 1 to5 carbon atoms, and a methyl group, an ethyl group, a propyl group, ann-butyl group or a tert-butyl group is particularly desirable.

The alkoxy group as the substituent is preferably an alkoxy group having1 to 5 carbon atoms, more preferably a methoxy group, ethoxy group,n-propoxy group, iso-propoxy group, n-butoxy group or tert-butoxy group,and most preferably a methoxy group or an ethoxy group.

Examples of the halogen atom for the substituent include a fluorineatom, a chlorine atom, a bromine atom and an iodine atom, and a fluorineatom is preferable.

Examples of the halogenated alkyl group for the substituent includegroups in which part or all of the hydrogen atoms within theaforementioned alkyl groups has been substituted with the aforementionedhalogen atoms.

The cyclic aliphatic hydrocarbon group may have part of the carbon atomsconstituting the ring structure thereof substituted with a substituentcontaining a hetero atom. As the substituent containing a hetero atom,—O—, —C(═O)—O—, —S—, —S(═O)₂— or —S(═O)₂—O— is preferable.

Aromatic Hydrocarbon Group for Ya²¹

The aromatic hydrocarbon group is a hydrocarbon group having at leastone aromatic ring.

The aromatic ring is not particularly limited, as long as it is a cyclicconjugated compound having (4n+2)π electrons, and may be eithermonocyclic or polycyclic. The aromatic ring preferably has 5 to 30carbon atoms, more preferably 5 to 20, still more preferably 6 to 15,and most preferably 6 to 12. Here, the number of carbon atoms within asubstituent(s) is not included in the number of carbon atoms of thearomatic hydrocarbon group. Examples of the aromatic ring includearomatic hydrocarbon rings, such as benzene, naphthalene, anthracene andphenanthrene; and aromatic hetero rings in which part of the carbonatoms constituting the aforementioned aromatic hydrocarbon rings hasbeen substituted with a hetero atom. Examples of the hetero atom withinthe aromatic hetero rings include an oxygen atom, a sulfur atom and anitrogen atom.

Specific examples of the aromatic hetero ring include a pyridine ringand a thiophene ring.

Specific examples of the aromatic hydrocarbon group include a group inwhich two hydrogen atoms have been removed from the aforementionedaromatic hydrocarbon ring or aromatic hetero ring (arylene group orheteroarylene group); a group in which two hydrogen atoms have beenremoved from an aromatic compound having two or more aromatic rings(biphenyl, fluorene or the like); and a group in which one hydrogen atomof the aforementioned aromatic hydrocarbon ring or aromatic hetero ringhas been substituted with an alkylene group (a group in which onehydrogen atom has been removed from the aryl group within theaforementioned arylalkyl group such as a benzyl group, a phenethylgroup, a 1-naphthylmethyl group, a 2-naphthylmethyl group, a1-naphthylethyl group, or a 2-naphthylethyl group, or a heteroarylalkylgroup). The alkylene group which is bonded to the aforementioned arylgroup or heteroaryl group preferably has 1 to 4 carbon atoms, morepreferably 1 or 2 carbon atoms, and most preferably 1 carbon atom.

With respect to the aromatic hydrocarbon group, the hydrogen atom withinthe aromatic hydrocarbon group may be substituted with a substituent.For example, the hydrogen atom bonded to the aromatic ring within thearomatic hydrocarbon group may be substituted with a substituent.Examples of substituents include an alkyl group, an alkoxy group, ahalogen atom, a halogenated alkyl group, and a hydroxyl group.

The alkyl group as the substituent is preferably an alkyl group of 1 to5 carbon atoms, and a methyl group, an ethyl group, a propyl group, ann-butyl group or a tert-butyl group is particularly desirable.

As the alkoxy group, the halogen atom and the halogenated alkyl groupfor the substituent, the same groups as the aforementioned substituentgroups for substituting a hydrogen atom within the cyclic aliphatichydrocarbon group can be used.

Divalent Linking Group Containing a Hetero Atom

In the case where Ya²¹ represents a divalent linking group containing ahetero atom, preferable examples of the linking group include —O—,—C(═O)—O—, —C(═O)—, —O—C(═O)—O—, —C(═O)—NH—, —NH—, —NH—C(═NH)— (may besubstituted with a substituent such as an alkyl group, an acyl group orthe like), —S—, —S(═O)₂—, —S(═O)₂—O—, and a group represented by generalformula: —Y²¹—O—Y²²—, —Y²¹—O—, —Y²¹—C(═O)—O—, —C(═O)—O—Y²¹,—[Y²¹—C(═O)—O]_(m″)—Y²²—, —Y²¹—O—C(═O)—Y²²— or —Y²¹—S(═O)₂—O—Y²²— [inthe formulae, Y²¹ and Y²² each independently represents a divalenthydrocarbon group which may have a substituent, O represents an oxygenatom, and m′ represents an integer of 0 to 3].

In the case where the divalent linking group containing a hetero atom is—C(═O)—NH—, —C(═O)—NH—C(═O)—, —NH— or —NH—C(═NH)—, H may be substitutedwith a substituent such as an alkyl group, an acyl group or the like.The substituent (an alkyl group, an acyl group or the like) preferablyhas 1 to 10 carbon atoms, more preferably 1 to 8, and most preferably 1to 5.

In general formulae —Y²¹—O—Y²²—, —Y²¹—O—, —Y²¹—C(═O)—O—, —C(═O)—O—Y²¹—,—[Y²¹—C(═O)—O]_(m″)—Y²²—, —Y²¹—O—C(═O)—Y²²— or —Y²¹—S(═O)₂—O—Y²²—, Y²¹and Y²² each independently represents a divalent hydrocarbon group whichmay have a substituent. Examples of the divalent hydrocarbon groupinclude the same groups as those described above as the “divalenthydrocarbon group which may have a substituent” in the explanation ofthe aforementioned divalent linking group.

As Y²¹, a linear aliphatic hydrocarbon group is preferable, morepreferably a linear alkylene group, still more preferably a linearalkylene group of 1 to 5 carbon atoms, and a methylene group or anethylene group is particularly desirable.

As Y²², a linear or branched aliphatic hydrocarbon group is preferable,and a methylene group, an ethylene group or an alkylmethylene group ismore preferable. The alkyl group within the alkylmethylene group ispreferably a linear alkyl group of 1 to 5 carbon atoms, more preferablya linear alkyl group of 1 to 3 carbon atoms, and most preferably amethyl group.

In the group represented by the formula —[Y²¹—C(═O)—O]_(m)″—Y²², m″represents an integer of 0 to 3, preferably an integer of 0 to 2, morepreferably 0 or 1, and most preferably 1. Namely, it is particularlydesirable that the group represented by the formula—[Y²¹—C(═O)—O]_(m)″-Y²²— is a group represented by the formula—Y²¹—C(═O)—O—Y²²—. Among these, a group represented by the formula—(CH₂)_(a′)—C(═O)—O—(CH₂)_(b′)— is preferable. In the formula, a′ is aninteger of 1 to 10, preferably an integer of 1 to 8, more preferably aninteger of 1 to 5, still more preferably 1 or 2, and most preferably 1.b′ is an integer of 1 to 10, preferably an integer of 1 to 8, morepreferably an integer of 1 to 5, still more preferably 1 or 2, and mostpreferably 1.

Ya²¹ preferably represents an ester bond [—C(═O)—O—], an ether bond(—O—), a linear or branched alkylene group, a combination of these, or asingle bond.

In the formula (a2-1), Ra²¹ represents a lactone-containing cyclicgroup, an —SO₂— containing cyclic group or a carbonate-containing cyclicgroup.

Preferable examples of the lactone-containing cyclic group, the —SO₂—containing cyclic group and the carbonate-containing cyclic group forRa²¹ include groups represented by general formulae (a2-r-1) to(a2-r-7), groups represented by general formulae (a5-r-1) to (a5-r-4)and groups represented by general formulae (ax3-r-1) to (ax3-r-3).

Among the above examples, a lactone-containing cyclic group or a —SO₂—containing cyclic group is preferable, and a group represented bygeneral formula (a2-r-1), (a2-r-2), (a2-r-6) or (a5-r-1) is morepreferable. Specifically, a group represented by any of chemicalformulae (r-lc-1-1) to (r-lc-1-7), (r-lc-2-1) to (r-lc-2-18),(r-lc-6-1), (r-sl-1-1) and (r-sl-1-18) is still more preferable.

As the structural unit (a2) contained in the component (A1), 1 kind ofstructural unit may be used, or 2 or more kinds may be used.

When the component (A1) includes the structural unit (a2), the amount ofthe structural unit (a2) based on the combined total (100 mol %) of allstructural units constituting the component (A1) is preferably 10 to 80mol %, more preferably 15 to 60 mol %, and still more preferably 20 to50 mol %.

When the amount of the structural unit (a2) is at least as large as thelower limit of the above preferable range, the effect of using thestructural unit (a2) can be satisfactorily achieved. On the other hand,when the amount of the structural unit (a2) is no more than the upperlimit of the above preferable range, a good balance can be achieved withthe other structural units, and various lithography properties andpattern shape can be improved.

(Structural Unit (a4))

The structural unit (a4) is a structural unit containing an acidnon-dissociable, aliphatic cyclic group.

When the component (A1) includes the structural unit (a4), dry etchingresistance of the resist pattern to be formed is improved. Further, thehydrophobicity of the component (A) is further improved. Increase in thehydrophobicity contributes to improvement in terms of resolution, shapeof the resist pattern and the like, particularly in a solvent developingprocess.

An “acid non-dissociable, aliphatic cyclic group” in the structural unit(a4) refers to a cyclic group which is not dissociated by the action ofthe acid (e.g., acid generated from the component (B) described later)upon exposure, and remains in the structural unit.

As the structural unit (a4), a structural unit which contains anon-acid-dissociable aliphatic cyclic group, and is also derived from anacrylate ester is preferable. As the cyclic group, any of the multitudeof conventional polycyclic groups used within the resin component ofresist compositions for ArF excimer lasers or KrF excimer lasers (andparticularly for ArF excimer lasers) can be used.

In consideration of industrial availability and the like, at least onepolycyclic group selected from amongst a tricyclodecyl group, adamantylgroup, tetracyclododecyl group, isobornyl group, and norbornyl group isparticularly desirable. These polycyclic groups may be substituted witha linear or branched alkyl group of 1 to 5 carbon atoms.

Specific examples of the structural unit (a4) include structural unitsrepresented by general formulae (a4-1) to (a4-7) shown below.

In the formulae, R^(α) is the same as defined above.

As the structural unit (a4) contained in the component (A1), 1 type ofstructural unit may be used, or 2 or more types may be used.

When the component (A1) includes the structural unit (a4), the amount ofthe structural unit (a4) based on the combined total of all structuralunits constituting the component (A1) is preferably 1 to 30 mol %, andmore preferably 3 to 20 mol %.

When the amount of the structural unit (a4) is at least as large as thelower limit of the above-mentioned preferable range, the effect of usingthe structural unit (a4) can be satisfactorily achieved. On the otherhand, when the amount of the structural unit (a4) is no more than theupper limit of the above-mentioned preferable range, a good balance canbe achieved with the other structural units.

The component (A) can be obtained, for example, by a conventionalradical polymerization or the like of the monomers corresponding witheach of the structural units, using a radical polymerization initiatorsuch as azobisisobutyronitrile (AIBN) or dimethyl2,2′-azobis(isobutyrate).

Furthermore, in the component (A1), by using a chain transfer agent suchas HS—CH₂—CH₂—CH₂—C(CF₃)₂—OH, a —C(CF₃)₂—OH group can be introduced atthe terminals of the component (A1). Such a copolymer having introduceda hydroxyalkyl group in which some of the hydrogen atoms of the alkylgroup are substituted with fluorine atoms is effective in reducingdeveloping defects and LER (line edge roughness:unevenness of the sidewalls of a line pattern).

In the present invention, the weight average molecular weight (Mw) (thepolystyrene equivalent value determined by gel permeationchromatography) of the component (A) is not particularly limited, but ispreferably 1,000 to 50,000, more preferably 1,500 to 30,000, and mostpreferably 2,000 to 20,000. When the weight average molecular weight isno more than the upper limit of the above-mentioned range, the resistcomposition exhibits a satisfactory solubility in a resist solvent. Onthe other hand, when the weight average molecular weight is at least aslarge as the lower limit of the above-mentioned range, dry etchingresistance and the cross-sectional shape of the resist pattern becomessatisfactory.

In the resist composition of the present invention, as the component(A), one type may be used, or two or more types of compounds may be usedin combination.

In the resist composition of the present invention, the amount of thecomponent (A) can be appropriately adjusted depending on the thicknessof the resist film to be formed, and the like.

<<Acid Generator Component; Component (B)>>

In the present embodiment, the acid generator component (B) includes anacid generator (B1) (hereafter, sometimes referred to as “component(B1)”) consisting of a compound represented by general formula (b1-1)shown below.

In the formula, R¹⁰¹ represents a hydrocarbon group having at least 1hydroxy group as a substituent; Y¹⁰¹ represents a single bond or adivalent linking group containing an oxygen atom; V¹⁰¹ represents asingle bond, an alkylene group or a fluorinated alkylene group; R¹⁰²represents a fluorine atom or a fluorinated alkyl group of 1 to 5 carbonatoms; and M′^(m+) represents an organic cation having a valency of m.

In formula (b1-1), R¹⁰¹ represents a hydrocarbon group having at least 1hydroxy group as a substituent. Examples of the hydrocarbon group forR¹⁰¹ include a cyclic group which may have a substituent, a chain alkylgroup which may have a substituent, and a chain alkenyl group which mayhave a substituent.

Cyclic Group which May have a Substituent for R¹⁰¹

The cyclic group is preferably a cyclic hydrocarbon group, and thecyclic hydrocarbon group may be either an aromatic hydrocarbon group oran aliphatic hydrocarbon group.

As the aromatic hydrocarbon group for R¹⁰¹, groups in which one hydrogenatom has been removed from an aromatic hydrocarbon ring described abovein relation to the divalent aromatic hydrocarbon group for Va¹ in theformula (a1-1) or an aromatic compound containing two or more aromaticring can be mentioned, and a phenyl group or a naphthyl group ispreferable.

As the cyclic aliphatic hydrocarbon group for R¹⁰¹, groups in which onehydrogen atom has been removed from a monocycloalkane or apolycycloalkane exemplified above in the explanation of the divalentaliphatic hydrocarbon group for Va¹ in the formula (a1-1) can bementioned, and an adamantyl group or a norbornyl group is preferable.

Further, the cyclic hydrocarbon group for R¹⁰¹ may contain a hetero atomlike as a heterocycle, and specific examples thereof includelactone-containing cyclic groups represented by the aforementionedgeneral formulas (a2-r-1) to (a2-r-7), —SO₂— containing cyclic groupsrepresented by the aforementioned formulas (a5-r-1) to (a5-r-4) andheterocyclic groups (r-hr-1) to (r-hr-16) shown below.

As the substituent for the cyclic hydrocarbon group for R¹⁰¹, an alkylgroup, an alkoxy group, a halogen atom, a halogenated alkyl group, ahydroxyl group, a carbonyl group, a nitro group or the like can be used.

The alkyl group as the substituent is preferably an alkyl group of 1 to5 carbon atoms, and a methyl group, an ethyl group, a propyl group, ann-butyl group or a tert-butyl group is particularly desirable.

The alkoxy group as the substituent is preferably an alkoxy group having1 to 5 carbon atoms, more preferably a methoxy group, ethoxy group,n-propoxy group, iso-propoxy group, n-butoxy group or tert-butoxy group,and most preferably a methoxy group or an ethoxy group.

Examples of the halogen atom for the substituent include a fluorineatom, a chlorine atom, a bromine atom and an iodine atom, and a fluorineatom is preferable.

Example of the aforementioned halogenated alkyl group includes a groupin which a part or all of the hydrogen atoms within an alkyl group of 1to 5 carbon atoms (e.g., a methyl group, an ethyl group, a propyl group,an n-butyl group or a tert-butyl group) have been substituted with theaforementioned halogen atoms.

Chain-Like Alkyl Group which May have a Substituent for R¹⁰¹

The chain-like alkyl group for R¹⁰¹ may be linear or branched.

The linear alkyl group preferably has 1 to 20 carbon atoms, morepreferably 1 to 15, and most preferably 1 to 10. Specific examplesinclude a methyl group, an ethyl group, a propyl group, a butyl group, apentyl group, a hexyl group, a heptyl group, an octyl group, a nonylgroup, a decyl group, an undecyl group, a dodecyl group, a tridecylgroup, an isotridecyl group, a tetradecyl group, a pentadecyl group, ahexadecyl group, an isohexadecyl group, a heptadecyl group, an octadecylgroup, a nonadecyl group, an icosyl group, a henicosyl group and adocosyl group.

The branched alkyl group preferably has 3 to 20 carbon atoms, morepreferably 3 to 15, and most preferably 3 to 10. Specific examplesinclude a 1-methylethyl group, a 1-methylpropyl group, a 2-methylpropylgroup, a 1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutylgroup, a 1-ethylbutyl group, a 2-ethylbutyl group, a 1-methylpentylgroup, a 2-methylpentyl group, a 3-methylpentyl group and a4-methylpentyl group.

Chain-Like Alkenyl Group which May have a Substituent for R¹⁰¹

The chain-like alkenyl group for R¹⁰¹ may be linear or branched, andpreferably has 2 to 10 carbon atoms, more preferably 2 to 5 carbonatoms, still more preferably 2 to 4 carbon atoms, and most preferably 3carbon atoms. Examples of linear alkenyl groups include a vinyl group, apropenyl group (an allyl group) and a butynyl group. Examples ofbranched alkenyl groups include a 1-methylpropenyl group and a2-methylpropenyl group.

Among the above-mentioned examples, as the chain-like alkenyl group, apropenyl group is particularly desirable.

As the substituent for the chain-like alkyl group or alkenyl group forR¹⁰¹, an alkoxy group, a halogen atom, a halogenated alkyl group, ahydroxyl group, a carbonyl group, a nitro group, an amino group, acyclic group for R¹⁰¹ or the like can be used.

Among these examples, as R¹⁰¹, a cyclic group which may have asubstituent is preferable, and a cyclic hydrocarbon group which may havea substituent is more preferable. Specifically, a phenyl group, anaphthyl group, a group in which one or more hydrogen atoms have beenremoved from a polycycloalkane, a lactone-containing cyclic grouprepresented by any one of the aforementioned formula (a2-r-1) to(a2-r-7), and an —SO₂— containing cyclic group represented by any one ofthe aforementioned formula (a5-r-1) to (a5-r-4).

In formula (b-1-1), Y¹⁰¹ represents a single bond or a divalent linkinggroup containing an oxygen atom.

In the case where Y¹⁰¹ is a divalent linking group containing an oxygenatom, Y¹⁰¹ may contain an atom other than an oxygen atom. Examples ofatoms other than an oxygen atom include a carbon atom, a hydrogen atom,a sulfur atom and a nitrogen atom.

Examples of divalent linking groups containing an oxygen atom includenon-hydrocarbon, oxygen atom-containing linking groups such as an oxygenatom (an ether bond; —O—), an ester bond (—C(═O)—O—), an oxycarbonylgroup (—O—C(═O)—), an amido bond (—C(═O)—NH—, —NH—C(═O)—), a carbonylgroup (—C(═O)—) and a carbonate bond (—O—C(═O)—O—); and combinations ofthe aforementioned non-hydrocarbon, hetero atom-containing linkinggroups with an alkylene group. Furthermore, the combinations may have asulfonyl group (—SO₂—) bonded thereto. As the combination, the linkinggroup represented by formulas (y-a1-1) to (y-a1-7) shown below can bementioned.

In the formulae, V′¹⁰¹ represents a single bond or an alkylene group of1 to 5 carbon atoms; V′¹⁰² represents a divalent saturated hydrocarbongroup of 1 to 30 carbon atoms.

The divalent saturated hydrocarbon group for V′¹⁰² is preferably analkylene group of 1 to 30 carbon atoms.

The alkylene group for V′¹⁰¹ and V′¹⁰² may be a linear alkylene group ora branched alkylene group, and a linear alkylene group is preferable.

Specific examples of the alkylene group for V′¹⁰¹ and V′¹⁰² include amethylene group [—CH₂—]; an alkylmethylene group, such as —CH(CH₃)—,—CH(CH₂CH₃)—, —C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)— and—C(CH₂CH₃)₂—; an ethylene group [—CH₂CH₂—]; an alkylethylene group, suchas —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂— and —CH(CH₂CH₃)CH₂—; atrimethylene group (n-propylene group) [—CH₂CH₂CH₂—]; analkyltrimethylene group, such as —CH(CH₃)CH₂CH₂— and —CH₂CH(CH₃)CH₂—; atetramethylene group [—CH₂CH₂CH₂CH₂—]; an alkyltetramethylene group,such as —CH(CH₃)CH₂CH₂CH₂—, —CH₂CH(CH₃)CH₂CH₂—; and a pentamethylenegroup [—CH₂CH₂CH₂CH₂CH₂—].

Further, part of methylene group within the alkylene group for V′¹⁰¹ andV′¹⁰² may be substituted with a divalent aliphatic cyclic group of 5 to10 carbon atoms. The aliphatic cyclic group is preferably a divalentgroup in which one hydrogen atom has been removed from the cyclicaliphatic hydrocarbon group for Ra′³ in the aforementioned formula(a1-r-1), and a cyclohexylene group, 1,5-adamantylene group or2,6-adamantylene group is preferable.

Y¹⁰¹ is preferably a divalent linking group containing an ether bond oran ester bond, and groups represented by the aforementioned formulas(y-a1-1) to (y-a1-5) are preferable.

In formula (b-1-1), V¹⁰¹ represents a single bond, an alkylene group ora fluorinated alkylene group. The alkylene group and the fluorinatedalkylene group for V¹⁰¹ preferably has 1 to 4 carbon atoms. Examples ofthe fluorinated alkylene group for V¹⁰¹ include a group in which part orall of the hydrogen atoms within the alkylene group for V¹⁰¹ have beensubstituted with fluorine. Among these examples, as V¹⁰¹, a single bondor a fluorinated alkylene group of 1 to 4 carbon atoms is preferable.

In formula (b-1-1), R¹⁰² represents a fluorine atom or a fluorinatedalkyl group of 1 to 5 carbon atoms. R¹⁰² is preferably a fluorine atomor a perfluoroalkyl group of 1 to 5 carbon atoms, and more preferably afluorine atom.

In formula (b1-1), M′^(m+) represents an organic cation having a valencyof m, preferably a sulfonium cation or an iodonium cation, and mostpreferably a cation represented by any one of formulae (ca-1) to (ca-4)shown below.

In the formulae, R²⁰¹ to R²⁰⁷, R²¹¹ and R²¹² each independentlyrepresents an aryl group, an alkyl group or an alkenyl group, providedthat two of R²⁰¹ to R²⁰³, R²⁰⁶ and R²⁰⁷, or R²¹¹ and R²¹² may bemutually bonded to form a ring with the sulfur atom; R²⁰⁸ and R²⁰⁹ eachindependently represents a hydrogen atom or an alkyl group of 1 to 5carbon atoms; R²¹⁰ represents an aryl group which may have asubstituent, an alkyl group which may have a substituent, an alkenylgroup which may have a substituent or an —SO₂— containing cyclic groupwhich may have a substituent; L²⁰¹ represents —C(═O)— or —C(═O)—O—; Y²⁰¹each independently represents an arylene group, an alkylene group or analkenylene group; x represents 1 or 2; and W²⁰¹ represents a linkinggroup having a valency of (x+1).

As the aryl group for R²⁰¹ to R²⁰⁷, R²¹¹ and R²¹², an unsubstituted arylgroup of 6 to 20 carbon atoms can be mentioned, and a phenyl group or anaphthyl group is preferable.

The alkyl group for R²⁰¹ to R²⁰⁷, R²¹¹ and R²¹² is preferably achain-like or cyclic alkyl group having 1 to 30 carbon atoms.

The alkenyl group for R²⁰¹ to R²⁰⁷, R²¹¹ and R²¹² preferably has 2 to 10carbon atoms.

Specific examples of the substituent which R²⁰¹ to R²⁰⁷ and R²¹⁰ to R²¹²may have include an alkyl group, a halogen atom, a halogenated alkylgroup, a carbonyl group, a cyano group, an amino group, an aryl group,an arylthio group and groups represented by formulae (ca-r-1) to(ca-r-7) shown below.

The aryl group within the arylthio group as the substituent is the sameas defined for R¹⁰¹, and specific examples include a phenylthio groupand a biphenylthio group.

In the formulae, R′²⁰¹ each independently represents a hydrogen atom, acyclic group which may have a substituent, a chain-like alkyl groupwhich may have a substituent or a chain-like alkenyl group which mayhave a substituent.

As the cyclic group which may have a substituent, the chain-like alkylgroup which may have a substituent and the chain-like alkenyl groupwhich may have a substituent for R′²⁰¹, the same groups as thosedescribed above for R¹⁰¹ can be mentioned. As the cyclic group which mayhave a substituent and chain-like alkyl group which may have asubstituent, the same groups as those described above for the aciddissociable group represented by the aforementioned formula (a1-r-2) canbe also mentioned.

When R²⁰¹ to R²⁰³, R²⁰⁶, R²⁰⁷, R²¹¹ and R²¹² are mutually bonded to forma ring with the sulfur atom, these groups may be mutually bonded via ahetero atom such as a sulfur atom, an oxygen atom or a nitrogen atom, ora functional group such as a carbonyl group, —SO—, —SO₂—, —SO₃—, —COO—,—CONH— or —N(R_(N))— (wherein R_(N) represents an alkyl group of 1 to 5carbon atoms). The ring containing the sulfur atom in the skeletonthereof is preferably a 3 to 10-membered ring, and most preferably a 5to 7-membered ring. Specific examples of the ring formed include athiophene ring, a thiazole ring, a benzothiophene ring, a thianthrenering, a benzothiophene ring, a dibenzothiophene ring, a 9H-thioxanthenering, a thioxanthone ring, a thianthrene ring, a phenoxathiin ring, atetrahydrothiophenium ring, a tetrahydrothiopyranium ring and athioxanium ring.

R²⁰⁸ and R²⁰⁹ each independently represents a hydrogen atom or an alkylgroup of 1 to 5 carbon atoms, preferably a hydrogen atom or an alkylgroup of 1 to 3 carbon atoms, and when R²⁰⁸ and R²⁰⁹ each represents analkyl group, R²⁰⁸ and R²⁰⁹ may be mutually bonded to form a ring.

R²¹⁰ represents an aryl group which may have a substituent, an alkylgroup which may have a substituent, an alkenyl group which may have asubstituent, or an —SO₂— containing cyclic group which may have asubstituent.

Examples of the aryl group for R²¹⁰ include an unsubstituted aryl groupof 6 to 20 carbon atoms, and a phenyl group or a naphthyl group ispreferable.

As the alkyl group for R²¹⁰, a chain-like or cyclic alkyl group having 1to 30 carbon atoms is preferable.

The alkenyl group for R²¹⁰ preferably has 2 to 10 carbon atoms.

As the —SO₂— containing cyclic group for R²¹⁰ which may have asubstituent, the same “—SO₂— containing cyclic groups” as thosedescribed above may be mentioned, and a group represented by theaforementioned general formula (a5-r-1) is preferable.

Each Y²⁰¹ independently represents an arylene group, an alkylene groupor an alkenylene group.

Examples of the arylene group for Y²⁰¹ include groups in which onehydrogen atom has been removed from an aryl group given as an example ofthe aromatic hydrocarbon group for R¹⁰¹ in the aforementioned formula(b-1).

The alkylene group and the alkenylene group for Y²⁰¹ is the same asdefined for the aliphatic hydrocarbon group as the divalent linkinggroup represented by Va¹ in the aforementioned general formula (a1-1).

In the formula (ca-4), x represents 1 or 2.

W²⁰¹ represents a linking group having a valency of (x+1), i.e., adivalent or trivalent linking group.

As the divalent linking group for W²⁰¹, a divalent hydrocarbon groupwhich may have a substituent is preferable, and as examples thereof, thesame hydrocarbon groups as those described above for Ya²¹ in the generalformula (a2-1) can be mentioned. The divalent linking group for W²⁰¹ maybe linear, branched or cyclic, and cyclic is more preferable. Amongthese, an arylene group having two carbonyl groups, each bonded to theterminal thereof is preferable. Examples of the arylene group include aphenylene group and a naphthylene group, and a phenylene group isparticularly desirable.

As the trivalent linking group for W²⁰¹, a group in which one hydrogenatom has been removed from the aforementioned divalent linking group forW²⁰¹ and a group in which the divalent linking group has been bonded toanother divalent linking group can be mentioned. The trivalent linkinggroup for W²⁰¹ is preferably a group in which 2 carbonyl groups arebonded to an arylene group.

Specific examples of preferable cations represented by formula (ca-1)include cations represented by formulae (ca-1-1) to (ca-1-66) shownbelow.

In the formulae, g1, g2 and g3 represent recurring numbers, wherein g1is an integer of 1 to 5, g2 is an integer of 0 to 20, and g3 is aninteger of 0 to 20.

In the formulae, R″²⁰¹ represents a hydrogen atom or a substituent, andas the substituent, the same groups as those described above forsubstituting R²⁰¹ to R²⁰⁷ and R²¹⁰ to R²¹² can be mentioned.

Specific examples of preferable cations represented by formula (ca-3)include cations represented by formulae (ca-3-1) to (ca-3-6) shownbelow.

Specific examples of preferable cations represented by formula (ca-4)include cations represented by formulae (ca-4-1) and (ca-4-2) shownbelow.

In the present embodiment, the component (B1) preferably consists of acompound represented by general formula (b1-1-1) shown below.

In the formula, R″¹⁰¹ represents an aliphatic cyclic group having atleast 1 hydroxy group as a substituent; L″¹⁰¹ represents —C(═O)— or—SO₂—; V″¹⁰¹ represents a fluorinated alkylene group; v″ represents aninteger of 0 to 3; q″ represents an integer of 1 to 20; n″ represents 0or 1; and M′^(m+) represents an organic cation having a valency of m.

In formula (b1-1-1), R″¹⁰¹ represents an aliphatic cyclic group havingat least 1 hydroxy group as a substituent. The aliphatic cyclic groupfor R″¹⁰¹ is preferably any of examples of the cyclic aliphatichydrocarbon group for R¹⁰¹, more preferably an adamantyl group or anorbornyl group, and still more preferably an adamantyl group. As thesubstituent, the same groups as those described above for substitutingthe cyclic aliphatic hydrocarbon group for R¹⁰¹ may be mentioned.

In formula (b1-1-1), V″¹⁰¹ represents a fluorinated alkyl group. Thefluorinated alkyl group for V″¹⁰¹ is preferably a fluorinated alkylenegroup having 1 to 5 carbon atoms, more preferably —CF₂—, —CF₂CF₂—,—CHFCF₂—, —CF(CF₃)CF₂— or —CH(CF₃)CF₂—, and still more preferably—CHFCF₂—.

In formula (b1-1-1), v″ represents an integer of 0 to 3, and ispreferably 0.

In formula (b1-1-1), q″ represents an integer of 1 to 20, preferably aninteger of 1 to 10, more preferably an integer of 1 to 3, and still morepreferably 2.

In formula (b1-1-1), n″ is 0 or 1, and is preferably 0.

In formula (b1-1-1), M′^(m+) represents an organic cation having avalency of m, and is the same as defined for M′^(m+) in theaforementioned formula (b1-1).

As the component (B1), 1 kind of these acid generators may be usedalone, or 2 or more kinds may be used in combination.

In the component (B), the amount of the component (B1) is preferably 50%by weight or more, and more preferably 60% by weight or more.

In the present embodiment, the component (B) may contain an acidgenerator other than the component (B1) (hereafter, referred to as“component (B2)”).

As the component (B2), there is no particular limitation, and any of theknown acid generators used in conventional chemically amplified resistcompositions can be used.

Examples of these acid generators are numerous, and include onium saltacid generators such as iodonium salts and sulfonium salts; oximesulfonate acid generators; diazomethane acid generators such as bisalkylor bisaryl sulfonyl diazomethanes and poly(bis-sulfonyl)diazomethanes;nitrobenzylsulfonate acid generators; iminosulfonate acid generators;and disulfone acid generators. Among these, it is preferable to use anonium salt acid generator.

As the onium salt acid generator, a compound represented by generalformula (b-1) below (hereafter, sometimes referred to as “component(b-1)”), a compound represented by general formula (b-2) below(hereafter, sometimes referred to as “component (b-2)”) or a compoundrepresented by general formula (b-3) below (hereafter, sometimesreferred to as “component (b-3)”) may be used.

In the formulae, R¹⁰¹′ and R¹⁰⁴ to R¹⁰⁸ each independently represents acyclic group which may have a substituent, a chain-like alkyl groupwhich may have a substituent or a chain-like alkenyl group which mayhave a substituent, provided that R¹⁰⁴ and R¹⁰⁵ may be mutually bondedto form a ring; two of R¹⁰⁶ to R¹⁰⁸ may be mutually bonded to form aring; R¹⁰² represents a fluorine atom or a fluorinated alkyl group of 1to 5 carbon atoms; Y¹⁰¹ represents a single bond or a divalent linkinggroup containing an oxygen atom; V¹⁰¹ to V¹⁰³ each independentlyrepresents a single bond, an alkylene group or a fluorinated alkylenegroup; L¹⁰¹ and L¹⁰² each independently represents a single bond or anoxygen atom; L¹⁰³ to L¹⁰⁵ each independently represents a single bond,—CO— or —SO₂—; and M′^(m+) represents an organic cation having a valencyof m.

{Anion Moiety}

Anion Moiety of Component (b-1)

In formula (b-1), R¹⁰¹′ represents a cyclic group which may have asubstituent, a chain-like alkyl group which may have a substituent or achain-like alkenyl group which may have a substituent, and is the sameas defined for the a cyclic group which may have a substituent, achain-like alkyl group which may have a substituent or a chain-likealkenyl group which may have a substituent for R¹⁰¹ in theaforementioned formula (b1-1).

In formula (b-1), Y¹⁰¹, V¹⁰¹ and R¹⁰² are the same as defined for Y¹⁰¹,V¹⁰¹ and R¹⁰² in the aforementioned formula (b1-1).

As a specific example of the anion moiety for the component (b-1), inthe case where Y¹⁰¹ a single bond, a fluorinated alkylsulfonate anionsuch as a trifluoromethanesulfonate anion or a perfluorobutanesulfonateanion can be mentioned; and in the case where Y¹⁰¹ represents a divalentlinking group containing an oxygen atom, anions represented by formulae(an-1) to (an-3) shown below can be mentioned.

In the formulae, R″¹⁰¹ represents an aliphatic cyclic group which mayhave a substituent, a group represented by any one of the aforementionedformulae (r-hr-1) to (r-hr-6) or a chain-like alkyl group which may havea substituent; R″¹⁰² represents an aliphatic cyclic group which may havea substituent, a lactone-containing cyclic group represented by any oneof the aforementioned general formulae (a2-r-1) to (a2-r-7) or an —SO₂—containing cyclic group represented by any one of the aforementionedgeneral formulae (a5-r-1) to (a5-r-4); R″¹⁰³ represents an aromaticcyclic group which may have a substituent, an aliphatic cyclic groupwhich may have a substituent or a chain-like alkenyl group which mayhave a substituent; V″¹⁰¹ represents a fluorinated alkylene group; L″¹⁰¹represents —C(═O)— or —SO₂—; v″ represents an integer of 0 to 3; q″represents an integer of 1 to 20; and n″ represents 0 or 1.

As the aliphatic cyclic group for R″¹⁰¹, R″¹⁰² and R″¹⁰³ which may havea substituent, the same groups as the cyclic aliphatic hydrocarbon groupfor R¹⁰¹ described above are preferable. As the substituent, the samegroups as those described above for substituting the cyclic aliphatichydrocarbon group for R¹⁰¹ can be mentioned.

As the aromatic cyclic group for R″¹⁰³ which may have a substituent, thesame groups as the aromatic hydrocarbon group for the cyclic hydrocarbongroup represented by R¹⁰¹ described above are preferable. Thesubstituent is the same as defined for the substituent for the aromatichydrocarbon group represented by R¹⁰¹.

As the chain-like alkyl group for R″¹⁰¹ which may have a substituent,the same groups as those described above for R¹⁰¹ are preferable. As thechain-like alkenyl group for R″¹⁰³ which may have a substituent, thesame groups as those described above for R¹⁰¹ are preferable. V″¹⁰¹ ispreferably a fluorinated alkylene group of 1 to 3 carbon atoms, and mostpreferably —CF₂—, —CF₂CF₂—, —CHFCF₂—, —CF(CF₃)CF₂— or —CH(CF₃)CF₂—.

Anion Moiety of Component (b-2)

In formula (b-2), R¹⁰⁴ and R¹⁰⁵ each independently represents a cyclicgroup which may have a substituent, a chain-like alkyl group which mayhave a substituent or a chain-like alkenyl group which may have asubstituent, and is the same as defined for R¹⁰¹ in formula (b-1). R¹⁰⁴and R¹⁰⁵ may be mutually bonded to form a ring.

As R¹⁰⁴ and R¹⁰⁵, a chain-like alkyl group which may have a substituentis preferable, and a linear or branched alkyl group or a linear orbranched fluorinated alkyl group is more preferable.

The chain-like alkyl group preferably has 1 to 10 carbon atoms, morepreferably 1 to 7 carbon atoms, and still more preferably 1 to 3 carbonatoms. The smaller the number of carbon atoms of the chain-like alkylgroup for R¹⁰⁴ and R¹⁰⁵, the more the solubility in a resist solvent isimproved. Further, in the chain-like alkyl group for R¹⁰⁴ and R¹⁰⁵, itis preferable that the number of hydrogen atoms substituted withfluorine atoms is as large as possible because the acid strengthincreases and the transparency to high energy radiation of 200 nm orless or electron beam is improved. The fluorination ratio of thechain-like alkyl group is preferably from 70 to 100%, more preferablyfrom 90 to 100%, and it is particularly desirable that the chain-likealkyl group be a perfluoroalkyl group in which all hydrogen atoms aresubstituted with fluorine atoms.

In formula (b-2), V¹⁰² and V¹⁰³ each independently represents a singlebond, an alkylene group or a fluorinated alkylene group, and is the sameas defined for V¹⁰¹ in formula (b-1).

In formula (b-2), L¹⁰¹ and L¹⁰² each independently represents a singlebond or an oxygen atom.

Anion Moiety of Component (b-3)

In formula (b-3), R¹⁰⁶ to R¹⁰⁸ each independently represents a cyclicgroup which may have a substituent, a chain-like alkyl group which mayhave a substituent or a chain-like alkenyl group which may have asubstituent, and is the same as defined for R¹⁰¹ in formula (b-1).

L¹⁰³ to L¹⁰⁵ each independently represents a single bond, —CO— or —SO₂—.

{Cation Moiety}

In formulae (b-1), (b-2) and (b-3), M′^(m+) represents an organic cationhaving a valency of m, and is the same as defined for M′^(m+) in theaforementioned formula (b1-1).

As the component (B2), 1 kind of these acid generators may be usedalone, or 2 or more kinds may be used in combination.

In the present embodiment, in the case where the component (B) containsthe component (B2), the amount of the component (B2) within thecomponent (B) is preferably 50% by weight or less, and more preferably30% by weight or less.

In the present embodiment, the amount of the component (B) relative to100 parts by weight of the component (A) is preferably 0.5 to 60 partsby weight, more preferably 1 to 30 parts by weight, and still morepreferably 1 to 15 parts by weight.

When the amount of the component (B) is within the above-mentionedrange, formation of a resist pattern can be satisfactorily performed.Further, by virtue of the above-mentioned range, when each of thecomponents are dissolved in an organic solvent, a uniform solution canbe obtained and the storage stability becomes satisfactory.

<<Other Components>>

In the present embodiment, the resist composition may further contain,in addition to the component (A), or in addition to the component (A)and (B), any other optional components.

Examples of the other components include the component (D), thecomponent (E), the component (F) and the component (S) described below.

Component (D):

In the present embodiment, the resist composition may further contain anacid diffusion control agent (hereafter, referred to as “component(D)”).

The component (D) functions as an acid diffusion control agent, i.e., aquencher which traps the acid generated from the component (B) and thelike upon exposure.

In the present embodiment, the component (D) may be a photodecomposablebase (D1) (hereafter, referred to as “component (D1)”) which isdecomposed upon exposure and then loses the ability of controlling ofacid diffusion, or a nitrogen-containing organic compound (D2)(hereafter, referred to as “component (D2)”) which does not fall underthe definition of component (D1).

Component (D1)

When a resist pattern is formed using a resist composition containingthe component (D1), the contrast between exposed portions and unexposedportions is improved.

The component (D1) is not particularly limited, as long as it isdecomposed upon exposure and then loses the ability of controlling ofacid diffusion. As the component (D1), at least one compound selectedfrom the group consisting of a compound represented by general formula(d1-1) shown below (hereafter, referred to as “component (d1-1)”), acompound represented by general formula (d1-2) shown below (hereafter,referred to as “component (d1-2)”) and a compound represented by generalformula (d1-3) shown below (hereafter, referred to as “component(d1-3)”) is preferably used.

At exposed portions, the components (d1-1) to (d1-3) are decomposed andthen lose the ability of controlling of acid diffusion (i.e., basicity),and therefore the components (d1-1) to (d1-3) cannot function as aquencher, whereas at unexposed portions, the components (d1-1) to (d1-3)functions as a quencher.

In the formulae, Rd¹ to Rd⁴ represent a cyclic group which may have asubstituent, a chain-like alkyl group which may have a substituent or achain-like alkenyl group which may have a substituent, provided that,the carbon atom adjacent to the sulfur atom within the Rd² in theformula (d1-2) has no fluorine atom bonded thereto; Yd¹ represents asingle bond or a divalent linking group; and M^(m+) each independentlyrepresents a cation having a valency of m.

{Component (d1-1)}

Anion Moiety

In formula (d1-1), Rd¹ represents a cyclic group which may have asubstituent, a chain-like alkyl group which may have a substituent or achain-like alkenyl group which may have a substituent, and is the samegroups as those defined above for R¹⁰¹.

Among these, as the group for Rd¹, an aromatic hydrocarbon group whichmay have a substituent, an aliphatic cyclic group which may have asubstituent and a chain-like hydrocarbon group which may have asubstituent are preferable. As the substituents which these groups mayhave, a fluorine atom or a fluorinated alkyl group is preferable.

The aromatic hydrocarbon group is preferably a phenyl group or anaphthyl group.

Examples of the aliphatic cyclic group include groups in which one ormore hydrogen atoms have been removed from a polycycloalkane such asadamantane, norbornane, isobornane, tricyclodecane ortetracyclododecane.

As the chain-like hydrocarbon group, a chain-like alkyl group ispreferable. The chain-like alkyl group preferably has 1 to 10 carbonatoms, and specific examples thereof include a linear alkyl group suchas a methyl group, an ethyl group, a propyl group, a butyl group, apentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl ora decyl group, and a branched alkyl group such as a 1-methylethyl group,a 1-methylpropyl group, a 2-methylpropyl group, a 1-methylbutyl group, a2-methylbutyl group, a 3-methylbutyl group, a 1-ethylbutyl group, a2-ethylbutyl group, a 1-methylpentyl group, a 2-methylpentyl group, a3-methylpentyl group or a 4-methylpentyl group.

In the case where the chain-like alkyl group is a fluorinated alkylgroup having a fluorine atom or a fluorinated alkyl group, thefluorinated alkyl group preferably has 1 to 11 carbon atoms, morepreferably 1 to 8 carbon atoms, and still more preferably 1 to 4 carbonatoms. The fluorinated alkyl group may contain an atom other thanfluorine. Examples of the atom other than fluorine include an oxygenatom, a carbon atom, a hydrogen atom, a sulfur atom and a nitrogen atom.

As Rd¹, a fluorinated alkyl group in which part or all of the hydrogenatoms constituting a linear alkyl group have been substituted withfluorine atom(s) is preferable, and a fluorinated alkyl group in whichall of the hydrogen atoms constituting a linear alkyl group have beensubstituted with fluorine atoms (i.e., a linear perfluoroalkyl group) ismore preferable.

Specific examples of preferable anion moieties for the component (d1-1)are shown below.

Cation Moiety

In formula (d1-1), M^(m+) represents an organic cation having a valencyof m.

The organic cation for M^(m+) is not particularly limited, and examplesthereof include the same cation moieties as those represented by theaforementioned formulas (ca-1) to (ca-4), and cation moietiesrepresented by the aforementioned formulas (ca-1-1) to (ca-1-66) arepreferable.

As the component (d1-1), one type of compound may be used, or two ormore types of compounds may be used in combination.

{Component (d1-2)}

Anion Moiety

In formula (d1-2), Rd² represents a cyclic group which may have asubstituent, a chain-like alkyl group which may have a substituent or achain-like alkenyl group which may have a substituent, and is the samegroups as those defined above for R¹⁰¹,

provided that, the carbon atom adjacent to the sulfur atom within Rd²group has no fluorine atom bonded thereto (i.e., the carbon atomadjacent to the sulfur atom within Rd² group does not substituted with afluorine atom). As a result, the anion of the component (d1-2) becomesan appropriately weak acid anion, thereby improving the quenchingability of the component (D).

As Rd², an aliphatic cyclic group which may have a substituent ispreferable, and a group in which one or more hydrogen atoms have beenremoved from adamantane, norbornane, isobornane, tricyclodecane,tetracyclododecane or camphor (which may have a substituent) is morepreferable.

The hydrocarbon group for Rd² may have a substituent. As thesubstituent, the same groups as those described above for substitutingthe hydrocarbon group (e.g., aromatic hydrocarbon group, aliphatichydrocarbon group) for Rd¹ in the formula (d1-1) can be mentioned.

Specific examples of preferable anion moieties for the component (d1-2)are shown below.

Cation Moiety

In formula (d1-2), M^(m+) is an organic cation having a valency of m,and is the same as defined for M^(m+) in the aforementioned formula(d1-1).

As the component (d1-2), one type of compound may be used, or two ormore types of compounds may be used in combination.

{Component (d1-3)}

Anion Moiety

In formula (d1-3), Rd³ represents a cyclic group which may have asubstituent, a chain-like alkyl group which may have a substituent or achain-like alkenyl group which may have a substituent, and is the samegroups as those defined above for R¹⁰¹, and a cyclic group containing afluorine atom, a chain-like alkyl group or a chain-like alkenyl group ispreferable. Among these, a fluorinated alkyl group is preferable, andmore preferably the same fluorinated alkyl groups as those describedabove for Rd¹.

In formula (d1-3), Rd⁴ represents a cyclic group which may have asubstituent, a chain-like alkyl group which may have a substituent or achain-like alkenyl group which may have a substituent, and is the samegroups as those defined above for R¹¹.

Among these, an alkyl group which may have substituent, an alkoxy groupwhich may have substituent, an alkenyl group which may have substituentor a cyclic group which may have substituent is preferable.

The alkyl group for Rd⁴ is preferably a linear or branched alkyl groupof 1 to 5 carbon atoms, and specific examples include a methyl group, anethyl group, a propyl group, an isopropyl group, an n-butyl group, anisobutyl group, a tert-butyl group, a pentyl group, an isopentyl group,and a neopentyl group. Part of the hydrogen atoms within the alkyl groupfor Rd⁴ may be substituted with a hydroxy group, a cyano group or thelike.

The alkoxy group for Rd⁴ is preferably an alkoxy group of 1 to 5 carbonatoms, and specific examples thereof include a methoxy group, an ethoxygroup, an n-propoxy group, an iso-propoxy group, an n-butoxy group and atert-butoxy group. Among these, a methoxy group and an ethoxy group arepreferable.

As the alkenyl group for Rd⁴, the same groups as those described abovefor R¹⁰¹ can be mentioned, and a vinyl group, a propenyl group (an allylgroup), a 1-methylpropenyl group and a 2-methylpropenyl group arepreferable. These groups may have an alkyl group of 1 to 5 carbon atomsor a halogenated alkyl group of 1 to 5 carbon atoms as a substituent.

As the cyclic group for Rd⁴, the same groups as those described abovefor R¹⁰¹ can be mentioned. Among these, as the cyclic group, analicyclic group (e.g., a group in which one or more hydrogen atoms havebeen removed from a cycloalkane such as cyclopentane, cyclohexane,adamantane, norbornane, isobornane, tricyclodecane ortetracyclododecane) or an aromatic group (e.g., a phenyl group or anaphthyl group) is preferable. When Rd⁴ is an alicyclic group, theresist composition can be satisfactorily dissolved in an organicsolvent, thereby improving the lithography properties. Alternatively,when Rd⁴ is an aromatic group, the resist composition exhibits anexcellent photoabsorption efficiency in a lithography process using EUVor the like as the exposure source, thereby resulting in the improvementof the sensitivity and the lithography properties.

In formula (d1-3), Yd¹ represents a single bond or a divalent linkinggroup.

The divalent linking group for Yd¹ is not particularly limited, andexamples thereof include a divalent hydrocarbon group (aliphatichydrocarbon group, or aromatic hydrocarbon group) which may have asubstituent and a divalent linking group containing a hetero atom. Assuch groups, the same divalent linking groups as those described abovefor Ya²¹ in the formula (a2-1) can be mentioned.

As Yd¹, a carbonyl group, an ester bond, an amide bond, an alkylenegroup or a combination of these is preferable. As the alkylene group, alinear or branched alkylene group is more preferable, and a methylenegroup or an ethylene group is still more preferable.

Specific examples of preferable anion moieties for the component (d1-3)are shown below.

Cation Moiety

In formula (d1-3), M^(m+) is an organic cation having a valency of m,and is the same as defined for M^(m+) in the aforementioned formula(d1-1).

As the component (d1-3), one type of compound may be used, or two ormore types of compounds may be used in combination.

As the component (D1), one type of the aforementioned components (d1-1)to (d1-3), or at least two types of the aforementioned components (d1-1)to (d1-3) can be used in combination.

The amount of the component (D1) relative to 100 parts by weight of thecomponent (A) is preferably within a range from 0.5 to 10 parts byweight, more preferably from 0.5 to 8 parts by weight, and still morepreferably from 1 to 8 parts by weight.

When the amount of the component (D1) is at least as large as the lowerlimit of the above-mentioned range, excellent lithography properties andexcellent resist pattern shape can be obtained. On the other hand, whenthe amount of the component (D1) is no more than the upper limit of theabove-mentioned range, sensitivity can be maintained at a satisfactorylevel, and through-put becomes excellent.

The production methods of the components (d1-1) and (d1-2) are notparticularly limited, and the components (d1-1) and (d1-2) can beproduced by conventional methods.

The amount of the component (D1) relative to 100 parts by weight of thecomponent (A) is preferably within a range from 0.5 to 10.0 parts byweight, more preferably from 0.5 to 8.0 parts by weight, and still morepreferably from 1.0 to 8.0 parts by weight. When the amount of at leastas large as the lower limit of the above-mentioned range, excellentlithography properties and excellent resist pattern shape can beobtained. On the other hand, when the amount of the component (D) is nomore than the upper limit of the above-mentioned range, sensitivity canbe maintained at a satisfactory level, and through-put becomesexcellent.

Component (D2)

The component (D) may contain a nitrogen-containing organic compound(D2) (hereafter, referred to as component (D2)) which does not fallunder the definition of component (D1).

The component (D2) is not particularly limited, as long as it functionsas an acid diffusion control agent, and does not fall under thedefinition of the component (D1). As the component (D2), any of theconventionally known compounds may be selected for use. Among these, analiphatic amine, particularly a secondary aliphatic amine or tertiaryaliphatic amine is preferable.

An aliphatic amine is an amine having one or more aliphatic groups, andthe aliphatic groups preferably have 1 to 12 carbon atoms.

Examples of these aliphatic amines include amines in which at least onehydrogen atom of ammonia (NH₃) has been substituted with an alkyl groupor hydroxyalkyl group of no more than 12 carbon atoms (i.e., alkylaminesor alkylalcoholamines), and cyclic amines.

Specific examples of alkylamines and alkylalcoholamines includemonoalkylamines such as n-hexylamine, n-heptylamine, n-octylamine,n-nonylamine, and n-decylamine; dialkylamines such as diethylamine,di-n-propylamine, di-n-heptylamine, di-n-octylamine, anddicyclohexylamine; trialkylamines such as trimethylamine, triethylamine,tri-n-propylamine, tri-n-butylamine, tri-n-hexylamine,tri-n-pentylamine, tri-n-heptylamine, tri-n-octylamine,tri-n-nonylamine, tri-n-decylamine, and tri-n-dodecylamine; and alkylalcohol amines such as diethanolamine, triethanolamine,diisopropanolamine, triisopropanolamine, di-n-octanolamine, andtri-n-octanolamine. Among these, trialkylamines of 5 to 10 carbon atomsare preferable, and tri-n-pentylamine and tri-n-octylamine areparticularly desirable.

Examples of the cyclic amine include heterocyclic compounds containing anitrogen atom as a hetero atom. The heterocyclic compound may be amonocyclic compound (aliphatic monocyclic amine), or a polycycliccompound (aliphatic polycyclic amine).

Specific examples of the aliphatic monocyclic amine include piperidine,and piperazine.

The aliphatic polycyclic amine preferably has 6 to 10 carbon atoms, andspecific examples thereof include 1, 5-diazabicyclo[4.3.0]-5-nonene,1,8-diazabicyclo[5.4.0]-7-undecene, hexamethylenetetramine, and1,4-diazabicyclo[2.2.2]octane.

Examples of other aliphatic amines includetris(2-methoxymethoxyethyl)amine, tris{2-(2-methoxyethoxy)ethyl}amine,tris{2-(2-methoxyethoxymethoxy)ethyl}amine,tris{2-(1-methoxyethoxy)ethyl}amine, tris{2-(1-ethoxyethoxy)ethyl}amine,tris{2-(1-ethoxypropoxy)ethyl}amine,tris[2-{2-(2-hydroxyethoxy)ethoxy}ethyl]amine and triethanolaminetriacetate, and triethanolamine triacetate is preferable.

Further, as the component (D2), an aromatic amine may be used.

Examples of aromatic amines include aniline, pyridine,4-dimethylaminopyridine, pyrrole, indole, pyrazole, imidazole andderivatives thereof, as well as diphenylamine, triphenylamine,tribenzylamine, 2,6-diisopropylaniline andN-tert-butoxycarbonylpyrrolidine.

As the component (D2), one type of compound may be used alone, or two ormore types may be used in combination.

The component (D2) is typically used in an amount within a range from0.01 to 5.0 parts by weight, relative to 100 parts by weight of thecomponent (A). When the amount of the component (D) is within theabove-mentioned range, the shape of the resist pattern and the postexposure stability of the latent image formed by the pattern-wiseexposure of the resist layer are improved.

As the component (D), one type of compound may be used, or two or moretypes of compounds may be used in combination.

In the present embodiment, when the resist composition contains thecomponent (D), the amount of the component (D) relative to 100 parts byweight of the component (A) is preferably within a range from 0.1 to 15parts by weight, more preferably from 0.3 to 12 parts by weight, andstill more preferably from 0.5 to 12 parts by weight.

When the amount of the component (D) is at least as large as the lowerlimit of the above-mentioned range, various lithography properties (suchas LWR) of the resist composition are improved. Further, a resistpattern having an excellent shape can be obtained. On the other hand,when the amount of the component (D) is no more than the upper limit ofthe above-mentioned range, sensitivity can be maintained at asatisfactory level, and through-put becomes excellent.

Component (E):

Furthermore, in the resist composition of the present embodiment, forpreventing any deterioration in sensitivity, and improving the resistpattern shape and the post exposure stability of the latent image formedby the pattern-wise exposure of the resist layer, at least one compound(E) (hereafter referred to as the component (E)) selected from the groupconsisting of an organic carboxylic acid, or a phosphorus oxo acid orderivative thereof may be added.

Examples of suitable organic carboxylic acids include acetic acid,malonic acid, citric acid, malic acid, succinic acid, benzoic acid, andsalicylic acid.

Examples of phosphorus oxo acids include phosphoric acid, phosphonicacid and phosphinic acid. Among these, phosphonic acid is particularlydesirable.

Examples of oxo acid derivatives include esters in which a hydrogen atomwithin the above-mentioned oxo acids is substituted with a hydrocarbongroup. Examples of the hydrocarbon group include an alkyl group of 1 to5 carbon atoms and an aryl group of 6 to 15 carbon atoms.

Examples of phosphoric acid derivatives include phosphoric acid esterssuch as di-n-butyl phosphate and diphenyl phosphate.

Examples of phosphonic acid derivatives include phosphonic acid esterssuch as dimethyl phosphonate, di-n-butyl phosphonate, phenylphosphonicacid, diphenyl phosphonate and dibenzyl phosphonate.

Examples of phosphinic acid derivatives include phosphinic acid estersand phenylphosphinic acid.

As the component (E), one type may be used alone, or two or more typesmay be used in combination.

The component (E) is typically used in an amount within a range from0.01 to 5.0 parts by weight, relative to 100 parts by weight of thecomponent (A).

Component (S):

In the present embodiment, the resist composition can be prepared bydissolving the materials for the resist composition in an organicsolvent (hereafter, frequently referred to as “component (S)”).

The component (S) may be any organic solvent which can dissolve therespective components to give a uniform solution, and one or more kindsof any organic solvent can be appropriately selected from those whichhave been conventionally known as solvents for a chemically amplifiedresist.

Examples thereof include lactones such as γ-butyrolactone; ketones suchas acetone, methyl ethyl ketone (MEK), cyclohexanone, methyl-n-pentylketone (2-heptanone), and methyl isopentyl ketone; polyhydric alcohols,such as ethylene glycol, diethylene glycol, propylene glycol anddipropylene glycol; compounds having an ester bond, such as ethyleneglycol monoacetate, diethylene glycol monoacetate, propylene glycolmonoacetate, and dipropylene glycol monoacetate; polyhydric alcoholderivatives including compounds having an ether bond, such as amonoalkylether (e.g., monomethylether, monoethylether, monopropyletheror monobutylether) or monophenylether of any of these polyhydricalcohols or compounds having an ester bond (among these, propyleneglycol monomethyl ether acetate (PGMEA) and propylene glycol monomethylether (PGME) are preferable); cyclic ethers such as dioxane; esters suchas methyl lactate, ethyl lactate (EL), methyl acetate, ethyl acetate,butyl acetate, methyl pyruvate, ethyl pyruvate, methylmethoxypropionate, and ethyl ethoxypropionate; aromatic organic solventssuch as anisole, ethylbenzylether, cresylmethylether, diphenylether,dibenzylether, phenetole, butylphenylether, ethylbenzene,diethylbenzene, pentylbenzene, isopropylbenzene, toluene, xylene, cymeneand mesitylene; and dimethylsulfoxide (DMSO).

These solvents can be used individually, or in combination as a mixedsolvent.

Among these, PGMEA, PGME, γ-butyrolactone and EL are preferable.

Further, among the mixed solvents, a mixed solvent obtained by mixingPGMEA with a polar solvent is preferable. The mixing ratio (weightratio) of the mixed solvent can be appropriately determined, taking intoconsideration the compatibility of the PGMEA with the polar solvent, butis preferably in the range of 1:9 to 9:1, more preferably from 2:8 to8:2.

Specifically, when EL or cyclohexanone is mixed as the polar solvent,the PGMEA:EL or cyclohexanone weight ratio is preferably from 1:9 to9:1, and more preferably from 2:8 to 8:2. Alternatively, when PGME ismixed as the polar solvent, the PGMEA:PGME weight ratio is preferablyfrom 1:9 to 9:1, more preferably from 2:8 to 8:2, and still morepreferably 3:7 to 7:3.

Further, as the component (S), a mixed solvent of at least one of PGMEAand EL with γ-butyrolactone is also preferable. The mixing ratio(former:latter) of such a mixed solvent is preferably from 70:30 to95:5.

The amount of the component (S) is not particularly limited, and isappropriately adjusted to a concentration which enables coating of acoating solution to a substrate In general, the organic solvent is usedin an amount such that the solid content of the resist compositionbecomes within the range from 1 to 20% by weight, and preferably from 2to 15% by weight.

If desired, other miscible additives can also be added to the resistcomposition of the present invention. Examples of such miscibleadditives include additive resins for improving the performance of theresist film, dissolution inhibitors, plasticizers, stabilizers,colorants, halation prevention agents, and dyes.

The resist composition of the present embodiment exhibits goodlithography properties such as resolution, exposure latitude (EL margin)and CDU. The reasons why these effects can be achieved has not beenelucidated yet, but are presumed as follows.

In the resist composition of the present embodiment, the component (B)contains the component (B1) consisting of a compound represented byformula (b1-1). In the component (B1), the group at the terminal of theanion moiety (R¹⁰¹) has a hydroxy group. Therefore, it is presumed thatthe component (B1) exhibits a shorter acid diffusion length than an acidgenerator having no hydroxy group at the terminal group of the anionmoiety thereof.

Further, in the resist composition of the present embodiment, thecomponent (A) contains the polymeric compound (A1) having 0 to 20 mol %of a structural unit (a3). In general, it is known that the aciddiffusion length can be shortened by introducing a structural unitcontaining a polar group-containing aliphatic hydrocarbon group into thebase component. However, as a result of the studies of the presentinventors, it has been found that, in the case of combining a basecomponent having a structural unit containing a polar group-containingaliphatic hydrocarbon group introduced with an acid generator having ashort acid diffusion length such as the component (B1), there is apossibility that the sensitivity of the resist composition isdeteriorated, fluctuation of deprotection occurs at exposed portions,and CDU is also deteriorated. It is presumed that, by making the amountof the structural unit (a3) as small as 0 to 20 mol %, variouslithography properties such as resolution, exposure latitude (EL margin)and CDU are improved.

(Method of Forming a Resist Pattern)

The method of forming a resist pattern according to the presentembodiment includes: forming a resist film on a substrate using a resistcomposition of the aforementioned embodiment; conducting exposure of theresist film; and developing the resist film to form a resist pattern.

The method for forming a resist pattern according to the presentembodiment can be performed, for example, as follows.

Firstly, a resist composition of the first aspect is applied to asubstrate using a spinner or the like, and a bake treatment (postapplied bake (PAB)) is conducted at a temperature of 80 to 150° C. for40 to 120 seconds, preferably 60 to 90 seconds, to form a resist film.

Following selective exposure of the thus formed resist film, either byexposure through a mask having a predetermined pattern formed thereon(mask pattern) using an exposure apparatus such an electron beamlithography apparatus or an EUV exposure apparatus, or by patterning viadirect irradiation with an electron beam without using a mask pattern,baking treatment (post exposure baking (PEB)) is conducted undertemperature conditions of 80 to 150° C. for 40 to 120 seconds, andpreferably 60 to 90 seconds.

Next, the resist film is subjected to a developing treatment. Thedeveloping treatment is conducted using an alkali developing solution inthe case of an alkali developing process, and a developing solutioncontaining an organic solvent (organic developing solution) in the caseof a solvent developing process. The method of forming a resist patternaccording to the present embodiment is particularly useful in the caseof a solvent developing process.

After the developing treatment, it is preferable to conduct a rinsetreatment. The rinse treatment is preferably conducted using pure waterin the case of an alkali developing process, and a rinse solutioncontaining an organic solvent in the case of a solvent developingprocess.

In the case of a solvent developing process, after the developingtreatment or the rinsing, the developing solution or the rinse liquidremaining on the pattern can be removed by a treatment using asupercritical fluid.

After the developing treatment or the rinse treatment, drying isconducted. If desired, bake treatment (post bake) can be conductedfollowing the developing.

In this manner, a resist pattern can be formed.

The substrate is not specifically limited and a conventionally knownsubstrate can be used. For example, substrates for electroniccomponents, and such substrates having wiring patterns formed thereoncan be used. Specific examples of the material of the substrate includemetals such as silicon wafer, copper, chromium, iron and aluminum; andglass. Suitable materials for the wiring pattern include copper,aluminum, nickel, and gold.

Further, as the substrate, any one of the above-mentioned substratesprovided with an inorganic and/or organic film on the surface thereofmay be used. As the inorganic film, an inorganic antireflection film(inorganic BARC) can be used. As the organic film, an organicantireflection film (organic BARC) and an organic film such as alower-layer organic film used in a multilayer resist method can be used.

Here, a “multilayer resist method” is method in which at least one layerof an organic film (lower-layer organic film) and at least one layer ofa resist film (upper resist film) are provided on a substrate, and aresist pattern formed on the upper resist film is used as a mask toconduct patterning of the lower-layer organic film. This method isconsidered as being capable of forming a pattern with a high aspectratio. More specifically, in the multilayer resist method, a desiredthickness can be ensured by the lower-layer organic film, and as aresult, the thickness of the resist film can be reduced, and anextremely fine pattern with a high aspect ratio can be formed.

The multilayer resist method is broadly classified into a method inwhich a double-layer structure consisting of an upper-layer resist filmand a lower-layer organic film is formed (double-layer resist method),and a method in which a multilayer structure having at least threelayers consisting of an upper-layer resist film, a lower-layer organicfilm and at least one intermediate layer (thin metal film or the like)provided between the upper-layer resist film and the lower-layer organicfilm (triple-layer resist method).

The wavelength to be used for exposure is not particularly limited andthe exposure can be conducted using radiation such as ArF excimer laser,KrF excimer laser, F₂ excimer laser, extreme ultraviolet rays (EUV),vacuum ultraviolet rays (VUV), electron beam (EB), X-rays, and softX-rays. The resist composition is effective for KrF excimer laser, ArF,EB or

EUV, and more effective for ArF excimer laser, EB or EUV.

The exposure of the resist film can be either a general exposure (dryexposure) conducted in air or an inert gas such as nitrogen, orimmersion exposure (immersion lithography).

In immersion lithography, the region between the resist film and thelens at the lowermost point of the exposure apparatus is pre-filled witha solvent (immersion medium) that has a larger refractive index than therefractive index of air, and the exposure (immersion exposure) isconducted in this state.

The immersion medium preferably exhibits a refractive index larger thanthe refractive index of air but smaller than the refractive index of theresist film to be exposed. The refractive index of the immersion mediumis not particularly limited as long as it satisfies the above-mentionedrequirements.

Examples of this immersion medium which exhibits a refractive index thatis larger than the refractive index of air but smaller than therefractive index of the resist film include water, fluorine-based inertliquids, silicon-based solvents and hydrocarbon-based solvents.

Specific examples of the fluorine-based inert liquids include liquidscontaining a fluorine-based compound such as C₃HCl₂F₅, C₄F₉OCH₃,C₄F₉OC₂H₅ or C₅H₃F₇ as the main component, which have a boiling pointwithin a range from 70 to 180° C. and preferably from 80 to 160° C. Afluorine-based inert liquid having a boiling point within theabove-mentioned range is advantageous in that the removal of theimmersion medium after the exposure can be conducted by a simple method.

As a fluorine-based inert liquid, a perfluoroalkyl compound in which allof the hydrogen atoms of the alkyl group are substituted with fluorineatoms is particularly desirable. Examples of these perfluoroalkylcompounds include perfluoroalkylether compounds and perfluoroalkylaminecompounds.

Specifically, one example of a suitable perfluoroalkylether compound isperfluoro(2-butyl-tetrahydrofuran) (boiling point 102° C.), and anexample of a suitable perfluoroalkylamine compound isperfluorotributylamine (boiling point 174° C.).

As the immersion medium, water is preferable in terms of cost, safety,environment and versatility.

As an example of the alkali developing solution used in an alkalideveloping process, a 0.1 to 10% by weight aqueous solution oftetramethylammonium hydroxide (TMAH) can be given.

As the organic solvent contained in the organic developing solution usedin a solvent developing process, any of the conventional organicsolvents can be used which are capable of dissolving the component (A)(prior to exposure). Specific examples of the organic solvent includepolar solvents such as ketone solvents, ester solvents, alcoholsolvents, nitrile solvents, amide solvents and ether solvents, andhydrocarbon solvents.

A ketone solvent is an organic solvent containing C—C(═O)—C within thestructure thereof. An ester solvent is an organic solvent containingC—C(═O)—O—C within the structure thereof. An alcohol solvent is anorganic solvent containing an alcoholic hydroxy group in the structurethereof. An “alcoholic hydroxy group” refers to a hydroxy group bondedto a carbon atom of an aliphatic hydrocarbon group. A nitrile solvent isan organic solvent containing a nitrile group in the structure thereof.An amide solvent is an organic solvent containing an amide group withinthe structure thereof. An ether solvent is an organic solvent containingC—O—C within the structure thereof.

Some organic solvents have a plurality of the functional groups whichcharacterizes the aforementioned solvents within the structure thereof.In such a case, the organic solvent can be classified as any type of thesolvent having the characteristic functional group. For example,diethyleneglycol monomethylether can be classified as either an alcoholsolvent or an ether solvent.

A hydrocarbon solvent consists of a hydrocarbon which may behalogenated, and does not have any substituent other than a halogenatom. Examples of the halogen atom include a fluorine atom, a chlorineatom, a bromine atom and an iodine atom, and a fluorine atom ispreferable.

As the organic solvent contained in the organic developing solution,among these, a polar solvent is preferable, and ketone solvents, estersolvents and nitrile solvents are preferable.

Examples of ketone solvents include 1-octanone, 2-octanone, 1-nonanone,2-nonanone, acetone, 4-heptanone, 1-hexanone, 2-hexanone, diisobutylketone, cyclohexanone, methylcyclohexanone, phenylacetone, methyl ethylketone, methyl isobutyl ketone, acetylacetone, acetonylacetone, ionone,diacetonylalcohol, acetylcarbinol, acetophenone, methyl naphthyl ketone,isophorone, propylenecarbonate, γ-butyrolactone and methyl amyl ketone(2-heptanone). Among these examples, as a ketone solvent, methyl amylketone (2-heptanone) is preferable.

Examples of ester solvents include methyl acetate, butyl acetate, ethylacetate, isopropyl acetate, amyl acetate, isoamyl acetate, ethylmethoxyacetate, ethyl ethoxyacetate, propylene glycol monomethyl etheracetate, ethylene glycol monoethyl ether acetate, ethylene glycolmonopropyl ether acetate, ethylene glycol monobutyl ether acetate,ethylene glycol monophenyl ether acetate, diethylene glycol monomethylether acetate, diethylene glycol monopropyl ether acetate, diethyleneglycol monoethyl ether acetate, diethylene glycol monophenyl etheracetate, diethylene glycol monobutyl ether acetate, diethylene glycolmonoethyl ether acetate, 2-methoxybutyl acetate, 3-methoxybutyl acetate,4-methoxybutyl acetate, 3-methyl-3-methoxybutyl acetate,3-ethyl-3-methoxybutyl acetate, propylene glycol monomethyl etheracetate, propylene glycol monoethyl ether acetate, propylene glycolmonopropyl ether acetate, 2-ethoxybutyl acetate, 4-ethoxybutyl acetate,4-propoxybutyl acetate, 2-methoxypentyl acetate, 3-methoxypentylacetate, 4-methoxypentyl acetate, 2-methyl-3-methoxypentyl acetate,3-methyl-3-methoxypentyl acetate, 3-methyl-4-methoxypentyl acetate,4-methyl-4-methoxypentyl acetate, propylene glycol diacetate, methylformate, ethyl formate, butyl formate, propyl formate, ethyl lactate,butyl lactate, propyl lactate, ethyl carbonate, propyl carbonate, butylcarbonate, methyl pyruvate, ethyl pyruvate, propyl pyruvate, butylpyruvate, methyl acetoacetate, ethyl acetoacetate, methyl propionate,ethyl propionate, propyl propionate, isopropyl propionate, methyl2-hydroxypropionate, ethyl 2-hydroxypropionate,methyl-3-methoxypropionate, ethyl-3-methoxypropionate,ethyl-3-ethoxypropionate and propyl-3-methoxypropionate. Among theseexamples, as an ester solvent, butyl acetate is preferable.

Examples of nitrile solvents include acetonitrile, propionitrile,valeronitrile, butyronitrile and the like.

If desired, the organic developing solution may have a conventionaladditive blended. Examples of the additive include surfactants. Thesurfactant is not particularly limited, and for example, an ionic ornon-ionic fluorine and/or silicon surfactant can be used.

As the surfactant, a non-ionic surfactant is preferable, and a non-ionicfluorine surfactant or a non-ionic silicon surfactant is morepreferable.

When a surfactant is added, the amount thereof based on the total amountof the organic developing solution is generally 0.001 to 5% by weight,preferably 0.005 to 2% by weight, and more preferably 0.01 to 0.5% byweight.

The developing treatment can be performed by a conventional developingmethod. Examples thereof include a method in which the substrate isimmersed in the developing solution for a predetermined time (a dipmethod), a method in which the developing solution is cast up on thesurface of the substrate by surface tension and maintained for apredetermined period (a puddle method), a method in which the developingsolution is sprayed onto the surface of the substrate (spray method),and a method in which the developing solution is continuously ejectedfrom a developing solution ejecting nozzle while scanning at a constantrate to apply the developing solution to the substrate while rotatingthe substrate at a constant rate (dynamic dispense method).

As the organic solvent contained in the rinse liquid used in the rinsetreatment after the developing treatment in the case of a solventdeveloping process, any of the aforementioned organic solvents containedin the organic developing solution can be used which hardly dissolvesthe resist pattern. In general, at least one solvent selected from thegroup consisting of hydrocarbon solvents, ketone solvents, estersolvents, alcohol solvents, amide solvents and ether solvents is used.Among these, at least one solvent selected from the group consisting ofhydrocarbon solvents, ketone solvents, ester solvents, alcohol solventsand amide solvents is preferable, more preferably at least one solventselected from the group consisting of alcohol solvents and estersolvents, and an alcohol solvent is particularly desirable.

The alcohol solvent used for the rinse liquid is preferably a monohydricalcohol of 6 to 8 carbon atoms, and the monohydric alcohol may belinear, branched or cyclic. Specific examples thereof include 1-hexanol,1-heptanol, 1-octanol, 2-hexanol, 2-heptanol, 2-octanol, 3-hexanol,3-heptanol, 3-octanol, 4-octanol and benzyl alcohol. Among these,1-hexanol, 2-heptanol and 2-hexanol are preferable, and 1 hexanol and2-hexanol are more preferable.

As the organic solvent, one kind of solvent may be used alone, or two ormore kinds of solvents may be used in combination. Further, an organicsolvent other than the aforementioned examples or water may be mixedtogether. However, in consideration of the development characteristics,the amount of water within the rinse liquid, based on the total amountof the rinse liquid is preferably 30% by weight or less, more preferably10% by weight or less, still more preferably 5% by weight or less, andmost preferably 3% by weight or less.

If desired, the rinse solution may have a conventional additive blended.Examples of the additive include surfactants. Examples of the additiveinclude surfactants. As the surfactant, the same surfactants as thosedescribed above can be mentioned, a non-ionic surfactant is preferable,and a non-ionic fluorine surfactant or a non-ionic silicon surfactant ismore preferable.

When a surfactant is added, the amount thereof based on the total amountof the rinse liquid is generally 0.001 to 5% by weight, preferably 0.005to 2% by weight, and more preferably 0.01 to 0.5% by weight.

The rinse treatment using a rinse liquid (washing treatment) can beconducted by a conventional rinse method. Examples of the rinse methodinclude a method in which the rinse liquid is continuously applied tothe substrate while rotating it at a constant rate (rotational coatingmethod), a method in which the substrate is immersed in the rinse liquidfor a predetermined time (dip method), and a method in which the rinseliquid is sprayed onto the surface of the substrate (spray method).

EXAMPLES

As follows is a description of examples of the present invention,although the scope of the present invention is by no way limited bythese examples.

<Synthesis of Polymer>

Polymers (A)-1 to (A)-8 represented by the following chemical formulae(A)-1 to (A)-8 respectively and polymers (A)-9 to (A)-14 represented bythe following chemical formula (A)-9 were synthesized by a conventionalmethod. The weight average molecular weight (Mw) and the molecularweight dispersity (Mw/Mn) determined by the polystyrene equivalent valueas measured by gel permeation chromatography (GPC) and the compositionalratios (ratio (molar ratio) of the respective structural units withinthe structural formula) of the copolymers as measured by ¹³C-NMR areshown in Table 1.

TABLE 1 Polymer Compositional ratio Mw Mw/Mn (A)-1 l/m = 50/50 8600 1.64(A)-2 l/m = 50/50 8700 1.69 (A)-3 l/m/n = 30/20/50 8300 1.59 (A)-4 l/m/n= 30/20/50 8200 1.62 (A)-5 l/m/n = 30/20/50 8100 1.59 (A)-6 l/m/n/o/p =20/20/20/30/10 8400 1.65 (A)-7 l/m/n/o/p = 20/20/20/30/10 8200 1.50(A)-8 l/m = 50/50 9600 1.78 (A)-9 l/m/n = 40/55/5 9400 1.87 (A)-10 l/m/n= 40/50/10 9800 1.81 (A)-11 l/m/n = 40/45/15 11400 1.71 (A)-12 l/m/n =40/40/20 8200 1.60 (A)-13 l/m/n = 35/40/25 8300 1.43 (A)-14 l/m/n =30/40/30 5600 1.77

<Production of Resist Composition>

The components shown in Table 2 were mixed together and dissolved toobtain each resist composition.

TABLE 2 Compo- Compo- Compo- Compo- Compo- nent (A) nent (B) nent (D)nent (F) nent (S) Example 1 (A)-1 (B)-1 (D)-1 (F)-1 (S)-1 [100] [9.4][3.1] [1.2] [3500] Comparative (A)-1 (B)-2 (D)-1 (F)-1 (S)-1 Example 1[100] [9.2] [3.1] [1.2] [3500] Comparative (A)-1 (B)-3 (D)-1 (F)-1 (S)-1Example 2 [100] [9.6] [3.1] [1.2] [3500] Comparative (A)-1 (B)-4 (D)-1(F)-1 (S)-1 Example 3 [100] [8.5] [3.1] [1.2] [3500] Example 2 (A)-2(B)-1 (D)-1 (F)-1 (S)-1 [100] [9.4] [3.1] [1.2] [3500] Example 3 (A)-3(B)-1 (D)-1 (F)-1 (S)-1 [100] [9.4] [3.1] [1.2] [3500] Example 4 (A)-4(B)-1 (D)-1 (F)-1 (S)-1 [100] [9.4] [3.1] [1.2] [3500] Example 5 (A)-5(B)-1 (D)-1 (F)-1 (S)-1 [100] [9.4] [3.1] [1.2] [3500] Example 6 (A)-6(B)-1 (D)-1 (F)-1 (S)-1 [100] [9.4] [3.1] [1.2] [3500] Example 7 (A)-7(B)-1 (D)-1 (F)-1 (S)-1 [100] [9.4] [3.1] [1.2] [3500] Example 8 (A)-8(B)-1 (D)-1 (F)-1 (S)-1 [100] [9.4] [3.1] [1.2] [3500] Example 9 (A)-9(B)-1 (D)-1 (F)-1 (S)-1 [100] [9.4] [3.1] [1.2] [3500] Example 10 (A)-10(B)-1 (D)-1 (F)-1 (S)-1 [100] [9.4] [3.1] [1.2] [3500] Example 11 (A)-11(B)-1 (D)-1 (F)-1 (S)-1 [100] [9.4] [3.1] [1.2] [3500] Example 12 (A)-12(B)-1 (D)-1 (F)-1 (S)-1 [100] [9.4] [3.1] [1.2] [3500] Comparative(A)-13 (B)-1 (D)-1 (F)-1 (S)-1 Example 4 [100] [9.4] [3.1] [1.2] [3500]Comparative (A)-14 (B)-1 (D)-1 (F)-1 (S)-1 Example 5 [100] [9.4] [3.1][1.2] [3500]

In Table 2, the reference characters indicate the following. The valuesin brackets [ ] indicate the amount (in terms of parts by weight) of thecomponent added.

(A)-1˜(A)-14: the aforementioned polymers (A)-1 to (A)-14

(B)-1: an acid generator represented by chemical formula (B)-1 shownbelow

(B)-2: An acid generator represented by chemical formula (B)-2 shownbelow

(B)-3: An acid generator represented by chemical formula (B)-3 shownbelow

(B)-4: An acid generator represented by chemical formula (B)-4 shownbelow

(D)-1: acid diffusion control agent represented by chemical formula(D)-1 below

(F)-1: fluorine-containing polymeric compound represented by chemicalformula (F)-1 below. The weight average molecular weight (Mw) and thedispersity (Mw/Mn) in terms of the polystyrene equivalent value measuredby gel permeation chromatography (GPC) were 15,500 and 1.66,respectively. The composition of the copolymer (ratio (molar ratio) ofthe respective structural units within the structural formula) asdetermined by ¹³C-NMR was 1/m=50/50.

(S)-1: a mixed solvent of propylene glycol monomethyl etheracetate/propylene glycol monomethyl ether/cyclohexanone=45/30/25 (weightratio)

[Formation of Resist Pattern]

An organic anti-reflection film composition (product name: ARC95,manufactured by Brewer Science Ltd.) was applied to an 12-inch siliconwafer using a spinner, and the composition was then baked at 205° C. for60 seconds and dried, thereby forming an organic anti-reflection filmhaving a film thickness of 90 nm.

Then, each of the resist compositions of Examples 1 to 12 andComparative Examples 1 to 5 was applied to the organic antireflectionfilm, and was then prebaked (PAB) on a hotplate at 110° C. for 60seconds and dried, thereby forming a resist film having a film thicknessof 85 nm.

Subsequently, the resist film was selectively irradiated with an ArFexcimer laser (193 nm) through a mask, using an immersion lithographyArF exposure apparatus NSR-S610C (manufactured by Nikon Corporation;Cross-pole (0.98/0.78)w/A-pol.; immersion medium: water).

Then, a post exposure bake (PEB) treatment was conducted at 110° C. for60 seconds.

Then, a solvent development was conducted for 30 seconds using butylacetate.

As a result, in each of the examples, a contact hole pattern (hereafter,referred to as “CH pattern”) having a hole diameter of 43 nm and a pitchof 90 nm (mask size: 63 nm) was formed.

[Evaluation of Optimum Exposure Dose (Eop)]

The optimum exposure dose Eop (mJ/cm²) with which the target CH patternwas formed in the above “formation of resist pattern” was determined.The results are indicated under “Eop (mJ/cm²)” in Table 3.

With respect to the exposure dose with which a CH pattern having holeswith a diameter of 43 nm are arranged at equal intervals (pitch: 90 nm)is formed, the exposure dose with which a CH pattern having a targetsize±5% is formed was formed was determined, and the EL margin (unit: %)was determined by the following formula. The results are indicated “5%EL (%)” in Table 3.EL margin (%)=(|E1−E2/Eop)×100

E1: Exposure dose (mJ/cm²) with which a CH pattern having a holediameter of 40.85 nm was formed

E2: Exposure dose (mJ/cm²) with which a CH pattern having a holediameter of 45.15 nm was formed

The larger the value of the “EL margin”, the smaller the change in thepattern size by the variation of the exposure dose.

[Evaluation of Resolution with Low Exposure Dose]

Using a scanning electron microscope S-9380 (manufactured by HitachiHigh-Technologies Corporation), the minimum resolution size (nm) wasdetermined by decreasing the exposure dose from the optimal exposuredose Eop with which a CH pattern having a hole diameter of 43 nm and apitch of 90 nm was formed. The results are indicated under “MinCD (nm)”in Table 3.

[Evaluation of in-Plane Uniformity (CDU) of Pattern Size]

With respect to each hole pattern obtained above, 100 holes in the CHpattern were observed from the upper side thereof using a lengthwisemeasuring scanning electron microscope (SEM) (product name: S-9380,manufactured by Hitachi High-Technologies Corporation; accelerationvoltage: 300V), and the hole diameter (nm) of each hole was measured.

From the results, the value of 3 times the standard deviation (σ) (3σ)was determined. The results are indicated under “CDU (nm)” in Table 3.

The smaller the thus determined 30 value is, the higher the level of thedimension uniformity (CD uniformity) of the holes formed in the resistfilm.

TABLE 3 Eop 5% EL Min CD CDU (mJ/cm²) (%) (nm) (nm) Example 1 39.4 7.732.5 3.7 Comparative 26.6 4.6 35.8 4.6 Example 1 Comparative 29.2 4.834.5 4.4 Example 2 Comparative 26.0 4.3 36.0 4.4 Example 3 Example 242.0 7.3 29.4 3.9 Example 3 37.8 6.6 32.8 3.9 Example 4 36.4 6.0 35.84.6 Example 5 36.5 6.1 34.9 4.5 Example 6 42.7 7.0 31.4 4.1 Example 747.0 8.2 35.8 4.2 Example 8 54.5 7.1 32.5 4.5 Example 9 57.4 7.5 33.84.5 Example 10 59.0 8.2 34.0 4.6 Example 11 62.7 8.3 34.6 4.6 Example 1268.5 9.3 35.3 4.7 Comparative 79.3 11.7 35.3 5.3 Example 4 Comparative82.9 12.0 37.0 5.3 Example 5

From the results shown in Table 3, it was confirmed that the resistcompositions of Examples 1 to 12 applying the present inventionexhibited good lithography properties.

While preferred embodiments of the invention have been described andillustrated above, it should be understood that these are exemplary ofthe invention and are not to be considered as limiting. Additions,omissions, substitutions, and other modifications can be made withoutdeparting from the spirit or scope of the present invention.Accordingly, the invention is not to be considered as being limited bythe foregoing description, and is only limited by the scope of theappended claims.

What is claimed is:
 1. A resist composition which generates acid uponexposure and exhibits changed solubility in a developing solution underaction of acid, the resist composition comprising: a base component (A)which exhibits changed solubility in a developing solution under actionof acid; and an acid generator (B) which generates acid upon exposure,wherein the base component (A) comprises a polymeric compound (A1)comprising 0 to 20 mol % of a structural unit (a3) containing a polargroup-containing aliphatic hydrocarbon group, and the acid generatorcomponent (B) comprises an acid generator (B1) consisting of a compoundrepresented by general formula (b1-1-1) shown below:

wherein R″¹⁰¹ represents an adamantyl group having at least 1 hydroxygroup as a substituent and no substituent other than the at least 1hydroxy group; L″¹⁰¹ represents —C(═O)— or —SO₂—; V″¹⁰¹ represents—CHFCF₂—; v″ represents an integer of 0 to 3; q″ represents an integerof 1 to 20; n″ represents 0; and M′^(m+) represents an organic cationhaving a valency of m.
 2. The resist composition according to claim 1,wherein the polymeric compound (A1) further comprises a structural unit(a1) containing an acid decomposable group that exhibits increasedpolarity by the action of acid.
 3. The resist composition according toclaim 1, wherein the polymeric compound (A1) further comprises astructural unit (a2) which contains a lactone-containing cyclic group,an —SO₂— containing cyclic group or a carbonate-containing cyclic group.4. The resist composition according to claim 2, wherein the polymericcompound (A1) further comprises a structural unit (a2) which contains alactone-containing cyclic group, an —SO₂— containing cyclic group or acarbonate-containing cyclic group.
 5. A method of forming a resistpattern, comprising: forming a resist film on a substrate using theresist composition of claim 1; exposing the resist film; and developingthe exposed resist film to form a resist pattern.